I think it has less to do with any culture, and just how the pay structure works for all the different things you mentioned. USPS/UPS/Fedex/bus/metro/train driv

I think it has less to do with any culture, and just how the pay structure works for all the different things you mentioned. USPS/UPS/Fedex/bus/metro/train drivers all make livable wages and have benefits. I'm not defending the tipping pay structure, but it's certainly not some confusing mystery.