I wondered about that many years ago. However, I do this; Take your NM and make sure it's empty. Next, cock the hammer. Look at the amount of firing pin coverage by the transfer bar. usually from 35% to 60% from the ones I have. Next, hold the hammer back and pull the trigger and watch the transfer bar. It rises up more when the trigger is pulled.
I just checked my 2 Lipsey's 44's and my Accusport 45 convertable. All 3 did exactly this same thing.
Basically, don't worry as there is more contact than you think.