Compared to outside the US, the US tipping culture is really bizarre. It's gotten to the point where baristas ask for a tip with their self checkout machines,

Compared to outside the US, the US tipping culture is really bizarre. It's gotten to the point where baristas ask for a tip with their self checkout machines, before they having even made a drink. Tips were never meant to make up a difference as you allege, especially not when "tipping" before service, which is not a tip, but a donation or bribe.