Easy there, tiger...
Firstly, there is parallel. The way the comment was made appeared to suggest that the level of care afforded to my luggage will be related to the level of the a priori payment. To an untrained eye that looks more like extortion, not a tip nor gratuity. Perhaps I was not sufficiently clear about the impression in my OP.

Re "only extremely cheap people" makes me wonder how many times @JonNYC has been outside of NYC, or more precisely outside of North America (a tipping paradise as a replacement for decent wages, BTW, but that is a topic for an OMNI discussion perhaps). You see, I gave you my disclaimer right at the top of my OP. What I did not mention, but will add now for your education is that I was connecting from EY business class AUH-JFK. EY picks up their J passengers from home and drops them off at the F/J wing of their AUH terminal, where one simply steps out of the car and walks into the terminal. Luggage automagically (i.e. via EY staff porters) is unloaded, placed on carts and follows you to the check-in position. Tips are not expected. Once when I offered one, it was refused. So... next time before you trash someone (yeah, "extremely cheap" fits in the category), consider that not everybody lives in your centre of the universe.

To all other responders, thanks! I had no idea these were contract skycaps, and not AA checkin staff. Lots of good info from all of you.