I'm all for sticking to the rules. They are arithmetic, so it's easy. I presume that anybody who can afford an air ticket can afford a tape measure.

The problem is never any one person or any one bag. It's the "size creep" which starts with an extra inch and winds up with 50% of pax carrying on a steamer trunk to jack hammer into the OH.

Publish the rules, stick to them and life is pretty easy. If you don't like the rules, fly someone else.