Meh, I'll never understand how people can do this outside of financial need. As soon as I graduated college I got my own apartment (in NYC). Definitely worth the money.
I guess it depends what sort of person you are. I always enjoyed having roommates, and would never want to live alone. I'm in my mid-30s and if I wasn't married I'd probably still live with roommates.
Imagine yourself stuck in the an apartment with a lease with 3 people you hate most. That's the worst case scenario.