I am assuming you are talking about the pull in the single action mode.

The trigger must also have enough engagement for the firearm to also operate in double action mode. If you remove too much material from the engagement angles it will not operate properly in double action.

You gotta also remember that when a gunsmith does a trigger job he is puting himself on the line if he removes too much material from the surfaces and you end up shooting someone because the triger pull was too light or didn't engage the sear enough.