I used to believe voting was pointless and made no difference. I even had a moral objection that voting would signal my acceptance of a social contract I didn't agree with. Now, I've realized that while it may make little difference, it can't hurt. And it doesn't take much of my time. I follow political events closely anyway, and try to read up on local events before the election.
As for the social contract bit, well, as was yelled at my friend Ry4an once, "You aren't special, princess!" It doesn't matter if I've agreed with the social contract. Society binds everyone to it. Fortunately, my society is still open to change. It's hard and takes a long time, but possible. So I have to do everything I can to help change society to be the way I think it should be. That includes voting for the canidates with policies I support.