Well I do not know how my experience can contribute to the topic but I am going to try anyway, when I first started roleplaying on another site on a more often basis I generally only made one character and made sure it was adaptable to the roleplay and for what I needed and it worked very well.
Later on, now it has gotten shall I say bad on other sites despite having the one character plan I made others over time through the one I stuck to has been used a lot more than others when I was getting serious and now at that point of seriousness before it went downhill and I was finding my serious footing roleplaying wise.
I'm sad to hear things like this becoming a lost art, I don't wanna rant on more things I feel is a lost art as well but I feel more characters helps to diverse yourself as a roleplayer or even one in multiple settings can help for some people.