Us clear water softie cave divers like them because they are small and neat, don?t clip themselves to other things accidentally easily and they?re stainless (rather than brass or Ali) and survive in the sea.
I admit there is a learning curve to operate them thick or dry gloves, but they are ok once you?ve mastered it. The small size means you can use them or the single version universally for everything. On my standard backmounted kit, I have them on primary reg, backup lights, primary lighthead, contents gauge, stage bottles and all the things in my pockets.
As for the original question, I?ve got one on my survey wetnotes (to secure them in a pocket) - maybe someone dropped them doing that.
Before anyone thinks these are useful for actual caving, don?t. Once some mud or silt gets behind the trigger/spring they are impossible to open. This can actually be quite dangerous if they are clipped to something metal that itself can?t be cut. If you look at anyone?s diving gear that?s properly thought out, there will be a soft link/tied cord where the bolt snap is attached to anything metal so it can be cut away if necessary.