Yeah I totally agree. There are so many RPs I didn't join simply because of not having any inspiration or time to figure out a backstory for a character. I personally like to develop that as the RP progresses.

The second thing I think is hard, especially in the case of forum based RPs like RPGuild, is PC interaction. Unless you're doing a collab post it is really hard to, for example, converse with another PC without reducing yourself to many short one paragraph posts.