Every additional member means more money for the gym, so it's in their best interests to amass as many members as possible. There's a cost, though: too many members, and the gym gets crowded; a crowded gym means unhappy members who are more likely to take their money elsewhere. That's why forgetting about your resolution to become the living embodiment of the Brawny Man is a win-win for the gym: they get your money, and not your presence.
This isn't just an overlooked quirk of the gym business model. Gyms know this fact well, and do their best to attract people who are likely to stop going. It's why they keep the sleek cardio equipment in front and the intimidating free weights hidden away in back—anyone can jump on a treadmill, whereas free weights require enough dedication to learn correct form and individual exercises. It's why they have free pizza and bagels, in extreme cases. Decades ago, gyms were intimidating places that looked not unlike dungeons, and therefore attracted mostly committed fitness buffs. "Once gyms started looking more like hotels, coffee shops and restaurants," says NPR, "People who weren't bodybuilders started feeling comfortable in gyms. The casual gymgoer was born."