My philosophy:
https://www.youtube.com/watch?v=M2_SjB016e4

Not some BS frame of mind like "Limo drivers don’t tip the bell boys"...which makes zero sense, neither of which are the customer. If I were the guy being driven by the limo driver, I'd tip the driver. If the bell boy took care of my bags, they'd get tipped too.

I tip the fueler, potable water guy/gal, lav guy/gal, guys/gals that grab bags.
Cheap people suck, and cheap pilots are the worst.