could just be that rp is a relatively small chunk of their leisure activities and for them it's just a thing they do with that character. i don't stick to one character for that long before moving to someone new, but i know i find it hard to play multiple characters at once these days (or even play/watch enough things to pick up as many characters as i used to) what with all the other shit i've taken on, so i just play one character in various games/memes