A few random thoughts on medicals.
First, anyone who has been around GA for a few decades knows guys who are flying who absolutely, positively can NOT have a valid medical. And we aren't talking Champ-flyers -- I know a guy right now who is an absolute mess, medically, who continues to fly a personal twin turbine.
Second, anyone who thinks that many doctors who demand cash on the barrel head (insurance and credit cards need not apply) are actually reporting that income needs to buy some swampland I've got for sale. These 15-minute medicals (for $125) represent their fun, off-the-books money.
Finally, if your family's support depends on your medical, you have a huge incentive to live a healthier lifestyle -- and a huge disincentive to report any health issues. And you'd have to be completely nuts to report a mental health problem. (Pun intended.)
Nonetheless, overall, I would bet that the general health of airline pilots today is far better than it was in the heyday of airline travel. Those WWII boys all smoked, didn't exercise, didnt eat right, and they liked their liquor. After what they survived, who could blame them?
So, viewed in perspective, for commercial pilots the system generally works. For those of us who fly bug-smashers, IMHO it's a system that can be worked around by many, ignored by some, and is really nothing but a fun money generator for AMEs. YMMV.