As we know after the first double action shot is fired, the remaining shots are fired in single action...that is with a cocked hammer. One may well call...and it has been done...one of these pistols a self cocking pistol.
In any case, in the early days a great deal was made of decocking. Specially so by the early SIG Sauer trainers (salesmen masquerading as shooting instructors) whose main adversary in the market was Smith and Wesson with its slide mounted safety/decocking levers.
The story that the decocking levers were so easy to miss, and then the weapon would rendered inoperative, coupled with Copper's "don't get caught with your dingus down" helped fuels the fire for the SIG-esque decocking levers. Down and up was the mantra...even with Smith & Wessons.
But as market-driven instructors pushed decocking ASAP, the lore of the DA pistol became one of "decock as soon as possible after firing". I am against that notion and never adhered to it.
Here is my mantra - "Do not be a premature decocker".
I recall when I "ran the walls" (an old SWAT term) with my team, my S&W 5906 would be cocked if I was using it. Hammer went back as soon as the breaching began. When we ran them with MP5s, the team all went on Full Auto with finger in register. And you know what....nothing bad ever happened.
Some some "IFS"
If we agree that the trigger finger is the safety...and we either have it in register or on the trigger as needed.
If we agree that a single action shot is more accurate and easier to fire than a double action shot.
If we agree that the cocked DA/SA pistol is in essence the same as a striker fired pistol from an operational point of view...and that the striker fired pistol is just as safe as anything else.
Then we would agree that leaving the hammer cocked until the hostilities are over is a far better tactic than decocking the weapon due to a lack of self-trust.