Used to be the only real good argument for it I could see was that a new world with a new "race to the top" opened up those prestigious programs to new users, but with the loosened job restrictions and more movement and attrition, I don't think that holds much weight anymore either. I'd probably join, only because I'd want to be in on the race to the top - UCLA and Zone are the 2 programs I've not yet coached that I'd really like to, and this would be a good opportunity I guess. But at the same time, in the long run, it's not sustainably adding long term users to the game. Tweaking price structure and building an updated. balanced, and transparent game engine are the ways to do that.
All that said, I'd still be in favor of a new world right now if there was something unique about it (I don't mean like 4xday though, that's too much for me). Something like a hardcore world with more strict firing standards (at all levels, but especially high D1), and a career expiration of 50-60 seasons, with a forced "retirement" and restart at the bottom after a certain point. I'd be in for that, for sure.