the US has a culture where regulations and general social interactions are so pro-business that people blindly accept false advertising in the form of fees and taxes being tacked on after-the-fact rather than impose on businesses by asking them to name an all-in number.
it's not just tipping but also sales tax, restaurant "courtesy fees", airline fees, fuel surcharges, resort fees, electric surcharges (I pay more in fees than I do for the actual electricity!), auto sales bills, etc.
The US is allergic to the concept of having to advertise an out-the-door number, because that wouldn't make for compelling advertising, and that's the focus in the US.