The problem with "fitting the shooter to the gun" is that when:
1. Bird hunting and a grouse or covey flushes in the thick stuff, one does not have the luxury of carefully mounting the gun, placing the leading hand in just the right position, then checking to confirm that you are looking down (maybe slightly over) the rib.
2. When shooting 100 Sporting Clays targets, esp. in the heat of the summer, the shooter gets tired. If the gun doesn't fit (hits where he is looking without contortions) he's going to start missing targets.
IMHO even casual shooters like hitting targets more than missing targets.
But gun dealers are of course free to sell folks guns that don't fit, and try to convince them it doesn't matter if they would just fit themselves to the gun.
All true.
BTW I have no problems using lots of drop stocks because I'm tall with long arms and crawl the stock with the comb low on my face.
...though I'm also tall with long arms and I crawl the stock...but I can't shoot guns with lots of drop well at all...