ehhh, it can be complex. Where I live the minimum hourly wage is $20.00 U S dollars/hr. That's to flip hamburgers. Federal minimum wage is currently set @ $7.25 U S /hr. Each state has their own wage standards based on their economies. I live in California and it can be expensive to live here. The average monthly income is $29.69/hr. An single family home cost's $600,00.00 U S dollars. Across the state line I can purchase the same sq. footage home for $150 - 175 K less. The minimum wage in that state reflects that.
Now if your a server in a state where the cost of living is lower then the opposing state and you collect tips, your average reported income can be more than then where I live ( i e. cocktail waitress at Bellagio's in Las Vegas vs. a server at Ihop in L A) . Discretionary income; plays a big part in the U S economy, so much so; the the state and federal government doesn't want it to go away, they want to encourage it.
So what it comes down to is culture. The do's and the don'ts. The minimum wage in Australia is $15.17 /hr U S. , without tips, that's not fly in California. On the other hand if the tip/ gratuity is included in the bill, then we're still tippin'