It's next to impossible to get enough small bills to cover all the tipping you need to do on a vacation, between hotels and taxis, and other incidentals. ATMs typically spit out the local equivalent of USD$20s if you're lucky; US$100s if you're not. Who's going to make change for that?
At home this is less of a problem because (a) I don't have as many things to tip for, and (b) I have had time to save up small bills for tipping. But when first thrust into a foreign country you need to be PREPARED.
I've spent about six months in the USA, mostly on family holidays and business travel, and never knew it was expected to tip housekeeping.
Pay the staff a decent wage, or at least a fair wage, then charge me accordingly.
How do I put a tip on my work expenses?
https://www.nytimes.com/2017/10/30/business/hotel-housekeepe...
EDIT: I was wrong
Being UKian I didn't even know that this was a concept.
The hotel advertises a per-night fee, I pay it on departure.
Still felt bad when I checked out and still didn't have anything to leave.
That’s not any different than pizza delivery drivers, waiters, or car wash employees.
In any case, yeah, tipping your housekeeper is a common thing. Maybe not as common as I thought.