Reading this, I feel like I need to up my tipping in hotels for housekeeping. I always tip the bellman if needed, the valets, and the concierge if something exceptional is done. I do wish that more electronic options were available, since we increasingly have less cash on hand. I had a college job in a category that traditionally attracts trips, but since we were technically government affiliated workers, we had to turn them down. I had some nice tips I had to give back, too (like $60 in today's money).
Yes, in many European countries overtipping by Americans is an issue. We generally round up in France, or leave a few Euros. This includes taxis and Ubers. But it is more customary in a few situations, especially tours and restroom attendants. In other European countries, it varies widely but I think every place rounds up totals in restaurants, bars, taxis and cafes (and I've been to 28+). In the UK it is technically optional but has become notably more typical, to the point that you must ask to take off a service charge that is often added at nicer restaurants.
It is offensive in Japan. In others, it is more customary, and sometimes that customary expectations is reserved for foreigners. But typically in those situations, the disparity in income and costs makes the impact of a small tip even larger.
