I think it totally depends on your personality and particular situation. If you've got a partner and kids, you may not have much time for friends or even emotional need for them. If you're single, on the other hand, they can be a major thing in your life and a true lifesaver. Personally, I am fairly outgoing, and like to have some friends, I also feel that I need to have someone to talk to who can provide a different perspective than DH, and someone who's also a woman and understands and cares about hair cuts, pregnancy (actually being pregnant), and just generally being a woman. I always feel revived when 'I've seen good friends. I also think that sometimes friends can take some of the pressure of my relationship if I'm in a bad mood and I can vent to someone else than DH, so he doesn't always have to listen to it!
That said, like you, I have been massively disappointed in many friends over the time who've let me down in various ways, either suddenly not wanted to invest as much in the relationship as I did, or in various ways been selfish and uncaring. I guess I have very high expectations for friends, and always try to do my best with them, so if someone else doesn't it really hurts me. My position on the matter now is that I don't want to spend time or energy on people whose friendship I have to chase or struggle to hold on to, or people who are flaky and cancel often, or people who are selfish. If people want to be my frie3nd and treat me with respect, I am their friend, but whereas I in younger years had a very proactive attitude to friendship and loads of friends, I now have a lot fewer and more of a cautious and laid back attitude.