I think it's software is made with the American market in mind. And local businesses use it as is and profit.
There's no custom of tipping that much at any of these places, but I feel cheap just clicking the lowest (no tip) of 4 options. Maybe all the time I've lived in the US plays a role here but it seems like it might just be the decoy effect [1] applied to tipping. It will be interesting to see if consumers see this as a dark pattern and push back.