I must say, the reason for this was twofold. I mean, sure, we are guilty of paying for the service and not using it - but we are also guilty of only working out because we are paying for it.
One of the main reasons we choose not to pay more than $50 a month for a gym membership is not only our crazy schedule, but that we live 15-20 minutes away. With a child in daycare, we would be making an additional round trip to town in order to work out. And before you go telling me to just go during lunch, no way. I am a hair sweater through and through, and there is no way I can go to the gym and then straight back to the office, to a meeting, etc.
I buy workout DVDs to do at home. We like running outside, but when it gets too hot/cold/dark early, we did invest in a very nice treadmill