Not that it helps people who literally can't afford it... But dental "checkups" are primarily about doing the cleaning, which is for preventing issues before they get that big. Identifying existing issues is secondary, but the regular dental appointment is doing more actual work than your typical physical examination.

Which is why most dental plans cover regular cleanings entirely, but you need to pay out of pocket for any other work you want. They would rather pay the entire cleaning bill every 6 months than pay part of your root canal once.