You have a good point there. Why tip at all ??
If one does their job and does it well, do you need to reward them more than they ask.... other than saying.... keep the change ??
For the postman, UPS, FedEx, bank teller, Sushi chef, car salesman, plumber, sign maker, girl holds the SLOW/STOP sign for DOT, meter reader, toll booth attendant, internet provider, all of your vendors, all of your grocery checkout people and the list goes on............... who all do a job for an agreed upon pay scale.... why should we pay them more at certain times of the year, so the rest of the year, when we're complaining about how you want to save pennies on your next ink purchase, the next package that comes late... if at all, the used car that doesn't work a week later and whatever else..... where are you big tippers then ??
Look, I'm all for tipping, but only if the situation warrants it. Waitresses or waiters, bartenders, kid cutting the grass, errand boy, employees [
my employees.... not someone elses], but not someone already doing their job with a possible intention of extorting more money from you at a holiday.