Why the false / exaggerated depth readings on watches?

[BluePurpleRed]

I have been looking at watches recently I was reminded of my bugbear about depth readings. I see posts and info saying that 30m is suitable for splashing etc and not for swimming. 100m is OK for swimming / shower / snorkeling but no more.

I guess divers watches must be properly rated by ATM settings, but why the over exaggeration? I mean surely it would be better to have the X metre rating be true and then just lower it to 0.5m for showering etc from 30m, and the same with the 100m & 250m?

I guess people here will have a good answer!