Likely ’cause most ratings would be made up.
I worked at a place where I was charged with defining specs of POS equipment. “Point-of-sale”, but also the other kind, after I saw the innards.
Anyhoo, I asked for the test-spex. Min/max RH, max altitude, temp tests, etc. “Make ’em up.” Huh?? “Here’s what our competitors have for their equipment. Copy those spex.”
So pretty much everything was 10%/90% RH (non-condensing), –40°F to 120°F, 25,000ft ASL, etc.
Doubt the competitors did any tests on their equipment, either.
So… most lights have O-ring in the usual spots, rubber-boot switches, so they should be good for soaking rain and even dunking in a bucket or pool, but without actually paying $$$ to a test-lab to put actual light samples through actual tests, it ain’t happening. And O-rings wear, so those spex would only be good with new O-rings, not worn ones. The O-rings in my E03 pretty much turned to goo, and that’s with factory lube, nothing that I added. I don’t intend on dunking ’em anytime soon, but dropping one in a pool or into a toilet should be survivable (if yicky), even with the goo-ring.
A diving light, etc., with 2-3 O-rings should be that much more waterproof, but I doubt any are tested except informally.
Ask Markus to take one snorkelling.