I'm not seeing revolvers shooting tighter groups when used double-action either.
From the long time Smith & Wesson "Parts List, Instructions For Use, Maintenance, Specifications, Guarantee" provided with each revolver:
"In single action shooting the hammer is pulled or cocked to its extreme rearward position. The gun may then be fired by merely pressing the trigger. This type of shooting is used for deliberate fire where there is time to sight the gun carefully and squeeze the trigger in an unhurried fashion. It is also used in competitive shooting for not only slow fire, but also for timed fire, whereby 20 seconds are allowed for the firing of each 5 shots and rapid fire where 10 seconds are allowed for the firing of each 5 shots.
There is time even in rapid fire shooting for the deliberate handling of the gun in single action fashion just so long as the function is performed without loss of time and in a definite cadence whereby the cycle will be completed within the allotted time.
Where time or other circumstances do not allow for single action fire the revolver is used double action. To fire the revolver double action all that is necessary is to align the weapon with the object which you wish to hit and pull the trigger firmly to the rear. This will cause the hammer to rise to its full cocked position and then fall to explode the cartridge and as previously stated the only limit to the speed that the weapon can be manipulated in this fashion will be determined by the dexterity of the shooter. This type of shooting is required for combat work or under emergency conditions where the gun must be used with great speed."
I don't know when this narrative was first provided in the factory instruction sheet included with the revolvers or who wrote it, but it still applies today. If the factory took the trouble to cut a single action sear on the hammer to provide for that special goodness that is the Smith & Wesson single action trigger then I'm sure going to use it.
This notion that the Smith & Wesson revolver must be used "all double action, all the time" is a fallacy.
This false notion of only using the revolver double action seems to arisen with the internet firearms forum and a new generation of shooters who apparently don't know any better.