Also, the pill does sometimes fail. Rarely if you do things perfectly (99% succes), but since we're all human, things rarely go perfectly (91% succes rate in real life). If you normally have a cycle of bleeding once a month, you have a nice solid clue to go take a pregnancy test when you don't bleed once a month.

But yeah, you don't really HAVE to. My next period is planned for early 2026.