Think about it. On land, there are trees, cars, buildings, animals, people, rocks and lots of other things that the human eye must determine you are not when it is looking for you. Mottling can help you mimic the background by breaking up your outline; pattern recognition of shapes breaks down.
In the sky, what is there? Clouds, birds and well, planes. You’re one of those three. And until we make planes as big as clouds or as small as birds, it’s kind of hard to disguise what you are.
On the ocean, there is either land or a boat. A quick glance at a map will confirm what you are.
You use the paint pattern on the ship to confuse optical range finding. Contrasting angular patterns play havoc with depth perception and make it difficult to focus your rangefinder. Inaccurate range means inaccurate shots.
It’s not about hiding - that is what a submarine does. If you are within the horizon, you WILL be seen by human eyes! But you’ll at least make it hard to get an electronic range and target, and make it hard to get an optical range and target.
Of course, radar isn’t confused by paint which means the paint is there for human eyes and I’ve never seen a 90 degree wave. But then the Navy didn’t ask me so it’s mute.