Exactly. The world is not the US and the US is not the world. We obviously have that discussion regularly on the BA forum and several of the resident cabin crew are quite critical, and obviously, if one were to ask, say, JL cabin crew, they would be horrified at the idea.

It's worth noting that AA have fairly complex guidelines for crew on accepting cash or gift cards (essentially normally no but sometimes gift cards can be accepted etc) By contrast, several other airlines outside of the US explicitly forbid staff from accepting gifts, and some others don't regulate it at all.

Either way, I would have thought that as suggested above, if the goal is to be nice to crew, then those wanting to make a gift should have absolutely no issue giving it at the end of the flight rather than at the beginning, and if what some (non US?) crew dislike about those gifts is that when made at the beginning it isn ot always obvious whether this comes with some expectations, then again that would be resolved by the gift being given at the end of the flight, so it seems to me that giving any gift one has brought at the time of final descent is the way to go that gives the best of both worlds.