We always tip the skycap at least $2/bag; although in SLC we tipped her $5/bag. She was very friendly and helpful, and if I was going to over-tip someone it would have been her.

I really appreciate the convenience of curbside check-in so I hope people who do use it will remember to tip these people. It is so much easier than standing in those huge lines inside the terminal. At a time when people certainly need to maintain their current income levels I would not try to cut my own financial corners by failing to tip appropriately.