As a field watch enthusiast, I asked myself the same question. Most features of dive watches seemed useless and I prefer slimer watches.
That said, there's some benefits to that type of watch:
They're though. Water résistance wise, of course, but they're also quite shockproof.
The lume is generally superior.
The dive time bezel can be useful in every day situations, not only for diving.
If well designed, they're actually very comfortable, despite the thickness.
There's many ways to make a diver, from dressy to the most toolish. Everyone can find a model that suits his style.
Even with a smaller dial, they're very legible. At least the professional dive watches, since they must be able to tell the time in less than optimal conditions.
I bought a Seiko Turtle this January. Thick, large, quite heavy,... And I'm very reluctant to take it of my wrist. This case is a marvel of design, confort wise, and I love the styling. It's quickly becoming one of my favorite watches, alongside my Khaki Field King.