There's a couple of reasons I don't own an HDTV:
1) Input lag on HDTVs really bothers me. I have yet to really figure out how to make rhythm games work on an HDTV as effectively as I want them to.
2) Every time I have enough money to buy something expensive, TV is not my top priority. I play more PC games nowadays than console games and I don't watch a lot of TV, so TVs are a low priority for me. My PC is tricked out, and my PC's monitor is arguably better than my TV, which is exactly how I want it because I spend a lot more time looking at it.
I'm not like some kind of crazy anti-HDTV person who thinks all TVs should be CRT, HDTVs are nice, but I can't just go buy every nice thing I want and upgrading my TV is not high on my list.