I worked as a pizza delivery driver for several years. This unprofessional conduct is shameful. There’s no excuse for it. I don’t care if they didn’t get a tip.
A number of years ago I was going through MIA on my way to a flight. A luggage handler walked up and asked if he could assist, to which I said yes.
When we got to the counter I realized I did not have any bills, so I dug into my pocket and gave him a couple of bucks in change. (Generally at that time this was the standard “tip”.) (I will not tell you what part of town he was from, but they were all union.)
He muttered an obscene oath and threw the change on the ground at my feet (which a number of astonished bystanders noted).
From then on I have always carried my own luggage. If they think this advances them, they are extraordinarily stupid.