Now, when a watch says it can go 30 meters of depth, it can go that depth ONLY DURING THE WARRANTY PERIOD, for a certain amount of time. That's the new legal definition. So, theoretically, a scuba diver (scuba divers generally can go 18 meters deep or 30 meters deep) should be able to wear a Patek Philippe watch with 30 M water resistance while diving as long as the watch is new.
The problem is the average person who screws up their expensive watch blames the watch and never themselves. Heck, the average person who gets into a car accident blames the other car. We see the splinter in the other's eye before we see the twig in our own. And the watch companies can't eat all the costs. So, if we think from the watch producer's perspective (and not just our own consumer perspective), it's reasonable to see why the brands are quick to blame the consumer first.