I guess I'm confused here...

Are we talking about skycaps, the people with the carts that take your baggage and either take it to the outside counter or take it inside to the checkin line?

Because if so, I don't use Skycaps unless I have to go inside.

I DO use the curbside checkin. There is no fee for using curbside checkin. I tip $1 per bag, I have no idea what my wife tips, but lets say $2-4 for her. When we have a heavy bag, they usually look the other way when she tips.

It becomes an interesting situation with tipping. I tip valet's $1, unless I have to pay to valet park, in which case I tip $0-1 depending on the weather and speed of service.

I tip restaurant staff 12-15%. I do NOT tip maids, etc.

As far as I see it, if the staff member is paid on a tip based wage, then I will tip, otherwise I will not. Housekeeping staff are not paid on a tip based wage, nor, as far as I am aware, are paid valets.