I have not used it since I was around 16. I just stopped and decided to see if I smelled bad. I never really started smelling and I am 37 and haven't worn it since. I am a normal guy with a wife and friends and a solid office job. I am not a hippy or anything. I just don't think that smearing an absorbed chemical under my arms, right next to my lymph nodes, is a good thing to do every single day of my life.
I think it is easy for runners to skip deodorant because we sweat so much and then immediately shower. It would be harder to do if you just sat around all day and didn't sweat all of that offensive crap out of your body.
I sweat a ton when I run, but otherwise don't really need an underarm antiperspirant. If I was told that I smelled or noticed it myself, I would probably start using something... maybe Gold Bond or one of those Whole Foods deodorants, but my wife never complains...