Why does paying at the door protect a light gym user whose motivation vanishes for weeks?

Answer: Pay only at the door

Pay only at the door ✓ — Right. Pay-at-the-door keeps payment tied to actual attendance, so not going also stops spending. It feels less pleasant than a flat membership, but it protects uncertain users from converting a quiet month into a paid month.

Monthly with reminders — Not quite. Reminders can reduce forgetting, but they do not change the billing default. A monthly plan can still charge during a low-motivation stretch unless the user takes the extra step to cancel or pause.

Annual prepaid discount — Not quite. A prepaid discount can lower the sticker price, but it also moves the money upfront. That can motivate early visits, yet it does not protect a light user from paying during a later quiet stretch.