Tipping is also extremely inconsistent in at least three ways. One is the idea of a percentage: how does that make any sense? When I go out for a rare nice dinner and the tip alone ends up being $20 or so, I ask myself: did this person/restaurant really do any more than the server of the last entire meal that cost $20? Of course not, and yet somehow it would look weird to pay $40 for a $20 meal with tip, for the same…
But nowadays you're often expected to tip at beginning of meal (i.e., when you order and pay at register), and your tip is not tied to quality of service at all (and very often there isn't even any actual service, other than taking of order and preparation of food). As an older person this strikes me as bizarre; grew up in atmosphere where tips were always after meal and explicitly tied to quality of service.