I once had a checker call out to someone to "come over here and bag this s%$t." I asked "Bag this what? Doyou think I am paying my money for s*&t? No apology...nothing.
I take my own bags to the grocery. This is a problem in the self checkout lines as my bags don't weight the same as the grocery bags so someone has to come over and recalerbrate. Or I can put in their bags and then repack when I am done.
When I am in a checker line...I hand over my bags. They often proceed to put the groceries in plastic bags and then into my bags. Rather defeats the purpose. I prefer to bag myself.