That's like trusting a truck driver to not be sleep-deprived and high on drugs before he crashes, killing four police officers... but never mind. Let's go!
So are you saying that:
(1) the truck driver was not the subject of any compulsory periodic medical examination requirements, and
(2) if the truck driver had been subject to compulsory periodic medical examination requirements, the accident wouldn't have happened?
My understanding is that it's possible for a person who's been medically examined and certified as complying with a medical standard to be "sleep-deprived and high on drugs" a week after certification. Or the week after that. Or a day after that.
I do hope that those advocating for compulsory, periodic medical examinations are not so hypocritical as to take the risk of flying in Class G. There are plenty of 'self declared' pilots flying in G already - well, for decades actually - and they could be "sleep-deprived and high on drugs". (Don't tell anyone, but the same applies in some Class D.)