Springs
As it is said, there is no such thing as a free lunch.
Smith & Wesson revolvers don't have a trigger spring.
What the do have is a
rebound slide spring. It does two things, (1) it pushes the trigger back to the forward position, and (2) it rebounds the hammer so that the firing pin doesn't block the next cartridge as the cylinder turns, and doesn't rest against a primer.
If you go too far in using a lighter spring you may hang up the trigger while it is trying to rebound the hammer, or the trigger may not go fully forward to reset the cylinder stop, and if at this point you try to pull the trigger again the action will jam. "Short stroking," as it is called, can also happen when you are firing several fast shots in the double-action mode. While the trigger is easier to pull, it is also slower to return.
If a lighter spring would work
under any and all conditions, in any environment Smith & Wesson would use them. The fact that they don't should make one pause to think, "why not?"
The main reason the J-frame revolvers have heavy double-action trigger pulls is because they are... well... little. The relatively small trigger doesn't have the leverage that a larger one has to rotate the hammer backwards.
Professional gunsmiths that specialize in revolver work, as well as those doing similar adjustments at the factory, reduce trigger pull weight by eliminating unnecessary frictional resistance in both the cylinder assembly and the internal lockwork. They sometimes will do some minor work on the springs, but very little to next to none on any revolver that's intended to be used as a weapon.