That's not necessarily true, there are members here with 6oz triggers that shoot a lot and don't have problem. I dunno what the triggers and hammers are made of, but there have been speculations made by some members with metallurgy backgrounds that they're made of sintered steel. In any event, they aren't made of the same material they once were, if you read "Accurizing the Factory Rifle" by Mic McPherson, you'll see that he advocates using about 20lbs forward pressure on a cocked hammer and pulling the trigger to expedite wear and smooth the mating surfaces to lighten the trigger. There have been several members try that and broke the sear notch off of the hammer. I email Mic about this and he stated his work was on older H&Rs. So whatever they're made of, honing the trigger can result it too light of trigger and Perklo warns of that in his instructions, I've done 25-30 H&R triggers, only one has work lightened from ~2½lbs to 21oz, so going too light can have it's caveats.
Tim