I think people who buy them don't find them cumbersome enough to stop them from buying them. There are circumstances where I agree they stick out, like on a suit, but I wouldn't judge anyone for wearing one. Also heavy and cumbersome is very variable between models, the Seiko Shogun I mentioned is made out of titanium and therefor very light. If you find a watch cumbersome it's design has failed you, a well designed watch should never be cumbersome.

I agree that there are divers with very hard to read minute hands, then again, this is true of all watches. There are also divers with some of the easiest to read hands I've ever seen independent of aesthetics, the Omega Ocean Planet for example.

Nota Bene, diving bezels aren't used to measure remaining oxygen as far as I know, but to time the duration of your dive. Or of your boiling eggs, or of your meeting. Whatever really, it's just a very primitive chrono that's very hard to break.

A watch of any style can be made to any quality, you can find shit divers, and great dress watches. However I would argue that adding strength without adding weight will be hard or expensive. Movements are independent of style, but I'm under the assumption that making a very thin movement that's shock resistant is harder then making a slightly thicker one. Adding complications makes a watch inherently more susceptible to damage. Especially when it comes to water resistance in mechanical watches I suspect the compromises to make a case sleeker or thinner are hard to overcome.

To summarize, I don't think people find them that cumbersome or heavy. Bracelets can be switched for bands and in the higher end segment we find light options. I find minutes easier to read on most divers, though I agree there are some bad examples out there. Case in point: Lume. The Bezel rotates, you can use it for whatever you wish, or not use it at all. The point of a diver in my opinion is to be very durable, this does not mean other watches can't be. But the Diver design has it's advantages.

I'm not trying to convince you that you need a Diver, I'm merely trying to argue what it is that attracts other people to them. If you are actually planning on diving, you are much better off with a modern sophisticated diving computer in my opinion.