When I was in Cozumel last month I was the only one on the boat with some kind of a fully housed still camera and strobes. There was an occasional diver with a video camera (without lights), but the few others with cameras were the plastic case, no strobe little Canon or Olympus p+s style. I would estimate less than 10% of the divers I was with for the week had any kind of u/w camera.
I think the difference is that many people who go on vacation to dive, dive only on vacation and aren't hard core divers/photographers addicted to year-round diving and photography the way most of the Wetpixel audience is. If you look at Eric's d-camera poll in Wakatobi, I would say that most folks there are quite dedicated to diving and photography to travel so far to enjoy such a rich marine environment. But places like the Virgin Islands, Bahamas and much of the Carribean are get-a-way destinations for vacationers who like to dive, vs divers on vacation.
By comparison, the ratio of divers to cameras in the cold waters of British Columbia is much higher than any tropical trip I've been on. People don't come up here for a refreshing dip in 42 degree water, they come up to dive and photograph the rich marine life that thrives in the current swept walls and pinacles. I haven't been to Cocos or the Galapagos, but I bet the same is true on those trips as they are frequented by the more hard core divers vs the simple warm weather vacationers.