I rather work out at home or at a gym that has little people, you get a better sweat, don't have to wait on machines and you work out at your own pace without all the extra critics. I originally joined because I wanted to build more muscle mass and was there to support a friend that needed to loose weight for health reasons. I work out to be healthy (which I am), feel better about myself and to ensure my cloths fit.
I like cycling because it's a good sweat, you feel free and you feel less bond by constraints,10-20 miles is pretty easy and if you want to push yourself harder you can do more.
I know guys that use the gym to cruise for/ look at girls. I'll admit it makes me smile watching everyone working out and interacting, but without company don't really see myself being there. I would like to take up a contact sport though.