science

The yearly check up seems to be an American concept designed by a medical industry that make money the more often they have to see you. In countries with national health services you're more likely to just see a doctor as and when you need it.

Your americanism is showing :)

as the other commenter said, that's a somewhat uniquely american thing. I just visit the doctor when something is wrong with me. If there's nothing wrong, there's no need to go to the doctor.