Blumenkranz
Roll for INIT
The short answer is "because tragic stories are edgy, and edgy is cool".
The long answer is, amateur writers will gravitate towards tragic backstories because of several reasons. For example, expanding on the short answer, tragic stories tend to be shocking. Amateur writers often feel the need to "show off" to the rest of the community by making special snowflake characters with shocking and twisted backgrounds, something they feel will make them stand out over the rest of characters. This is also the reason why there are a lot of overpowered characters out there, because some amateur roleplayers love to take the protagonist spot and outperform other characters with lame generic and flashy powers.
Having a nice family, getting a degree, a decent paying job... you would essentially be an average person with a comfortable life with no shocking events on it. Being the child of a single mom, not having enough money to get to college, passing the rest of your days as a wage slave... darker, but still an average person with a mediocre life. However, killing both of your abusing parents, dropping high school and becoming a murderhobo? Oh well, now THAT's edgy, cool and unique! I mean, how many friends like that? None (I seriously hope you have none)? Yeah, thought so.
Truth is, nobody wants to ever make a bland character, unless the point of the character is being so bland it becomes interesting. However, other ways of making your character different from the rest is either making a unique non-edgy backstory, or demonstrating your uniqueness with your playstyle. Of course, these require a bit more of imagination or skill, respectively.
Other reason is it may be some sort of freeform minmaxing. Players tend to be more forgiving to characters with tragic pasts (yes, even the edgiest and murder-happy characters). Say, your character is some sort of human god, with a genius' intellect, all of the knowledge in the world, an expert in a thousand different martial arts (including some self-crafted ones), an incredible fit and athletic body and reality bending powers? Clearly, it must be some sort of Mary Sue, but... oh wait, your character has had a tragic past, so it's okay. You spent all your "freeform stat points" in your skills, so now you have to "cope" with a tragic backstory that will only bring all of the other player characters' attention to you. Clearly, this weight on your shoulders will compensate your absurdly overpowered abilities.
Finally, going along the lines of the first reason, I must add sad backstories are easy to write. When writing your character's biography, you tend to highlight only the most important points of its life, which often tend to be one (the plot hook or personal mission) or two, fluffed up to make them take more space than they should so it doesn't look like your biography is too short and risk getting the CS rejected.
With overtly tragic characters, you can simply write a list of all the bad shit that has happened to them (parents got murdered, so its actually the last of a kind, spent all its life in an orphanage or in the cold streets, had to rob or even murder to survive, recently lost its lover to the same person who murdered its parents, turns out it was its brother and had to murder him, etc) and with very little fluff you can build their whole life in a few short, concise and shocking sentences. That or simply expand to infinity that stream of events. Thing is, sad events are important events, and therefore a sad life will make a dense backstory that isn't disgustingly perfect. Since it isn't hard to imagine bad things and just connect them however, I assume that's the reason novice roleplayers prefer writing special snowflake tragic characters.
That or simply because shadows, blood and katanas are cool, of course.
The long answer is, amateur writers will gravitate towards tragic backstories because of several reasons. For example, expanding on the short answer, tragic stories tend to be shocking. Amateur writers often feel the need to "show off" to the rest of the community by making special snowflake characters with shocking and twisted backgrounds, something they feel will make them stand out over the rest of characters. This is also the reason why there are a lot of overpowered characters out there, because some amateur roleplayers love to take the protagonist spot and outperform other characters with lame generic and flashy powers.
Having a nice family, getting a degree, a decent paying job... you would essentially be an average person with a comfortable life with no shocking events on it. Being the child of a single mom, not having enough money to get to college, passing the rest of your days as a wage slave... darker, but still an average person with a mediocre life. However, killing both of your abusing parents, dropping high school and becoming a murderhobo? Oh well, now THAT's edgy, cool and unique! I mean, how many friends like that? None (I seriously hope you have none)? Yeah, thought so.
Truth is, nobody wants to ever make a bland character, unless the point of the character is being so bland it becomes interesting. However, other ways of making your character different from the rest is either making a unique non-edgy backstory, or demonstrating your uniqueness with your playstyle. Of course, these require a bit more of imagination or skill, respectively.
Other reason is it may be some sort of freeform minmaxing. Players tend to be more forgiving to characters with tragic pasts (yes, even the edgiest and murder-happy characters). Say, your character is some sort of human god, with a genius' intellect, all of the knowledge in the world, an expert in a thousand different martial arts (including some self-crafted ones), an incredible fit and athletic body and reality bending powers? Clearly, it must be some sort of Mary Sue, but... oh wait, your character has had a tragic past, so it's okay. You spent all your "freeform stat points" in your skills, so now you have to "cope" with a tragic backstory that will only bring all of the other player characters' attention to you. Clearly, this weight on your shoulders will compensate your absurdly overpowered abilities.
Finally, going along the lines of the first reason, I must add sad backstories are easy to write. When writing your character's biography, you tend to highlight only the most important points of its life, which often tend to be one (the plot hook or personal mission) or two, fluffed up to make them take more space than they should so it doesn't look like your biography is too short and risk getting the CS rejected.
With overtly tragic characters, you can simply write a list of all the bad shit that has happened to them (parents got murdered, so its actually the last of a kind, spent all its life in an orphanage or in the cold streets, had to rob or even murder to survive, recently lost its lover to the same person who murdered its parents, turns out it was its brother and had to murder him, etc) and with very little fluff you can build their whole life in a few short, concise and shocking sentences. That or simply expand to infinity that stream of events. Thing is, sad events are important events, and therefore a sad life will make a dense backstory that isn't disgustingly perfect. Since it isn't hard to imagine bad things and just connect them however, I assume that's the reason novice roleplayers prefer writing special snowflake tragic characters.
That or simply because shadows, blood and katanas are cool, of course.