As I said, tipping is in their blood, born to tip. Last time I was in USA - Hawaii - mid 2018, stayed in Waikikki, at the restaurants the bill had 3 boxes to tick for the tips, they were 15%, 20%, 25% I kid you not.
I recollect on Coral Princess Alaska Cruise a few years ago, were were in the lounge listening to piano music pre dinner, the pianist was asking for requests, so he got plenty of requests and many of the pax - Americans (because 95% of the pax were North Americans) got up and shoved a $10 bill in the pianist's pocket. Must have been a wealthy man that pianist, he was good but no Billy Joel, lol.