As far as I see it, schools should teach enough to keep you in a good baseline health and doctors are available if something comes up. What is done in a normal annual check up?
I think for growing kids it's probably a good thing -- if nothing else to be sure you're on schedule for various vaccines.
As an adult, I have regular dental care but I do not see an MD unless I am sick or injured. And "sick" does not include colds/sore throat -- there are good OTC meds for that.
For most people, if you feel "normal", aren't gaining or losing weight unexpectedly, don't tire more easily than normal, your blood pressure is OK, etc. your health is likely fine.
Disclaimer: I'm extrapolating from personal experience of a handful of countries, this of course doesn't necessarily apply to all of Europe.
I think the former stems from annual checkups in childhood.
Some insurance providers/employers, I suspect for preventative reasons against the latter category above, have started incentivizing annual physicals, so this may shift, but the whole US healthcare system is in such flux I wouldn't put money down on any outcome.
Edit: I pay for the additional blood panels
I guess a minority by population. I needed to make an appointment a couple years ago and the woman on the other end of the phone didn't really believe me that I didn't know where my medical records would be (in the past 10 years I'd had some stitches and a tetanus shot).