I dont think its laziness on part of the dealer/tire shop, but more of removing a liability from their shoulders.
You have to torque the wheel nuts to spec AND you have to redo them again after 100 miles or so. Not doing this second step increases the chances of lug nuts falling off.
How many people are going to go back to the dealer/tire shop to get them re-torqued? I'm going to say 0.
Because of this, the dealer/shop will over-torque. They dont want your wheel falling off.
I once went to a tire shop. I was happy when I saw the guy pull out the torque wrench. I was not happy when I saw him torque the crap out of the lug nuts.
Got home, loosen them up, put them up to spec. Two days later re-torqued.