Nemrod:[writing about divers using doubles for an 80' dive]
Is that sort of gear really needed for that dive?
Why not? Perhaps they have nitrox and want to extend their bottom time past where a single tank will take them. Who are you to tell them what's needed for their dive?
In the DIR-F class, you learn some good reasons to use doubles for a 100' dive, having to do with rock bottom, usable gas, and the like. I could see the same reasoning apply to 80', and though the reason gets a bit less compelling, it doesn't disappear altogether.
I've taken doubles on a dive where I never got below 30', just to practice trim, buoyancy and valve drills. Were the tanks needed to go to 30'? You might say no, but my practice would have been pointless without them, so I say they were needed.
I also know a lot of non-DIR divers who use doubles for non-penetration 80-100' wreck dives, sometimes for the same reasons the DIR divers do.