I don't agree. Like I don't want to see Lara Croft fucking Superman, or Dante fucking Sailor Moon. Just make your own characters and Superheroes and put them in your stories. There are unlimited assets to make whatever original character you want to make.
You may not, but others maybe?
For some people it's maybe just the chance to make those renders of characters that they like, like a commission but selfmade.
There is a reason why so many games have Fan Art Threads!
I for one, like to use premade characters from Games or know the basic assetts to recreater whatever i or others desire, but i also do create my own characters.
As long as there is a demand for something it will be done.
And also, a lot of people starting with that premade stuff and carry over to selfmade later on. For me it was easier to "play" with something that already existed and see/learn with the changes i made.
In the End.. it's "To Each, their own"