It may not surprise you that many gyms make a substantial about of their revenue from members who rarely or never show up to work out. This has been a bit of a secret to the industry and I learned this lesson quickly while I owned a significant investment in a gym in the Denver area.
Be honest with yourself and calculate a cost per use for your gym visits. Twice a month for a $30 gym is $15 per visit. Many gyms have a daily rate which you should make use of if the rate per use (times the number of visits) is lower than the monthly fee. Many members simply keep on paying because they constantly tell themselves, "well - maybe next week." Don't join them! Use the membership or cancel it -- it's just a senseable thing to do.