Well I guess you could think that way. Truth being, Im sure there may have been some negligent discharges, and maybe a few cocked revolvers pointed at suspects in the day. But Im sure that even real experts would agree that its hard to keep 8000 or so people from making a few mistakes, especially given all the different stressful situations that might occur, like holstering while running or fighting, anytime the gun might be accidently cocked without you knowing it. Or cocked to shoot, and then for some reason not fired and possibly holstered that way under stress.
And yes I know the trigger still has to be pressed. But please ask yourself, if you would carry a revolver cocked. If the answer is NO, then why ?, if you are sure YOU would never touch the trigger. I don't carry S/A autos even with a safety, but that's me.
Personally I think that back in the day, some very forward thinking police firearms instructors, determined that there was absolutely NO reason to have a single action capability on a revolver used for defensive reasons. Training proved that you could shoot faster and with just as much accuracy shooting double action only. So the S/A capability became a liability, especially in large revolvers with target hammers (model 14) that might be cocked inadvertently during a scuffle, while holstering with a jacket or coat on , in the seatbelt of a vehicle,(happened to me once with a Border Patrol type holster in my youth) or whatever. If you were never going to use it why have the possibility of it causing a problem.
Along with the fact that doing this would eliminate the issues caused by the few bonehead people you are always going to have ,(especially in large groups)that would be tempted to do things their way.
An addition bit , LAPD did not allow hammerless revolvers until the late 90s or so. Believe it or not this was a holdover due to the old practice of training with reloads. Officers were trained to pull the hammer back slightly and check their training ammo for high primers. I must confess that I ran every wadcutter through my gun in the same manner before every pistol match, even if it as factory ammo. Until I got old and lazy.