You said my name, so happy YvY
Personally, I find that history isn't always that important to a character. Although it can help to justify character traits, I just don't believe a lot of RPs have situations where a character's past is needed. Many RPs are about reacting to the here and now, it's fairly rare for the player to be able to plan the future for an RP, which also means it can be hard to fit in things that come from their past.
For example: Let's say your character's backstory is along the lines of "My father killed my family while I was at school, and when he was sent to jail he looked me in the eye and said 'You're next.'" Now the section would have the character's relationship with his family, perhaps school stuff, and what happened to him after, but a history like that would mean that the player would have to fit their father plot into the GMs plot. The more the RP focuses on story, the less the player can fit these things in, and the more irrelevant the history becomes (after all, why explicitly state history if it is just to justify the character's personality?) The history needs to contain story beats that are relevant to the plot that the character will go through, otherwise it is hard to see why it matters. The character's best story should be during the RP, not their past before it, but there's only so many histories one can have if they want to be unique there, when really players should try to have more average pasts, so they can have an amazing present.
That is pretty ranty, and certainly not well worded. I'm not against histories, in certain RPs they can be pretty cool (open sandbox ones for example), but as a universal thing I just don't buy into them. I think having RP samples are much more indicative of how a player wants to use their character and make them act in the world, and I bet players would be much more in-tune with their characters if these sample posts are joint posts with the GM, so that they have to have their character actually react to unexpected things.