Meh...I'm 28 and I have a lot of friends with roommates. In fact, most of them do even though they could live alone if they really wanted.
Many are only just getting to the point where they don't want them anymore. One is moving in with his GF soon and his roommate will be moving to a new place without roommates. Others have made murmors that living alone sounds like it might be nice but aren't willing to give up their apartments. My GF is moving to a studio (although, she lived with a consultant who was gone all week...and I can't remember the last weekend she wasn't at my place...so she basically lived alone).
They mostly all have good roommates that they know...not a ton of random craigslist jokers. Never heard of anyone complain that they can't get laid because of their roommates (and many who have gotten laid on account of roomates' freinds). When you are in NYC or the bay area and don't make piles of money, living alone sounds tough...and even here in cheap Chicago, I recognize that I have paid a lot of money over the years for the privilege of living alone.