It's a game ànd a workout thingy. You unlock bikes, wheels and routes. Only the jerseys and clothing are cosmetic. The more you ride, the better equipment you get. (And the more routes you can ride). I like that, it's fun and it gives me something to look forward to. If I had everything unlocked on day one Zwift would be a lot more boring and it would be just a training platform, like TR.
Anyway, @hippy isn't really the target demo I think. :) Not many people get on Zwift to do a vEverest as one of their first rides.