Well, sometimes yes and sometimes no. My wife is a diver and she gets a carry on also.
What good is arriving with regulators if my wing/BP and everything else is gone? I would rather get there with my camera, scuba junk is easier to replace than cameras and housings.
Besides, I could ask the same thing with the "cooler" guys, hard case or soft case, it is still the same size, volume, the only real variable is the weight, the hard cases are slightly heavier. Do you put your "regs" in the cooler with the camera?
N