No, its not than important, but I dare say it's more important than most of the other things being suggested.
This is a chess site after all, and such a variant would help it out. How often do you see new users complaining about how long their opponents take to move?
Blitz is different. I want to play correspondence chess, because I like the fact that I am able to use the analysis board and opening databases - I just want the option to play faster.
Like I said, if you don't want to play with those time controls, you don't have to use them.
The option is already there for touraments, so it's not like it would take huge amounts of work for the admins.