Great servers at high end restaurants are making 100K a year because of tips. Why would they want to make $20 an hour?
The 90th percentile wage for waiters (excluding fast-food!) is $20.46/hr. The 75th percentile is $14.73
https://www.bls.gov/oes/current/oes353031.htm
The vast majority of waiters would love to make a $20 wage.
Even if everyone at 4-dollar-sign restaurants was making 6 digits, that's still a small minority of restaurants.
In my experience only half of the population tips based on percentage, and it's generally those who eat at high end places, or seem to be more affluent. The rest tip based on "service" and that could be 5% on a $150 bill, or 20% on a $15 tab. I've seen both, and I think your example only applies to a very small percentage of wait staff.
I came from a food service background though and realize people have bad days, but it does put me in a bit of a conundrum on how to handle truly terrible service. Fortunately for my wallet, I don't frequent those upscale establishments so it's not a problem I think about often.
The person in the article though is in the back of the house. Those workers almost uniformly make minimum wage across the country.
[1] https://www.sfchronicle.com/food/article/Legendary-Zuni-Cafe...
The vast majority (let's call it 99%) of all dining establishments pay whatever their local tipped minimum wage is (for the purpose of this we'll use the Fed min, which is currently 2.13 with a "made whole" rate of 7.25). This means all the owner is on the hook for, is: 7.25 - 2.13 - Declared tip total.
What does this mean? It means sometimes waitstaff will actually have $0 paychecks, because the amount they earned actually outstrips the pay coming from their employer due to their tax burden on declared tips.
Well we can't have that! So what's an enterprising waiter to to? Often, declare as little as possible of their tips. Now you can't get away with ignoring credit card totals (there's a paper trail!) but you damn well better believe that every server (EVERY SERVER) everywhere in the country is doing their best to hide that cash from the tax man. Often times the managers help them with his (because they were usually servers too at some point).
TL;dr- Restaurants aren't paying servers who are making 20/hr. What's going on is that those places charge so much for their dining experience that it drives of tips (in the US, people typically tip as a percentage of their bill, e.g. 20 dollars on a 100 dollar meal is considered standard). It actually makes more sense for a restaurant to raise their prices if they want to their servers to make more money, and it STILL doesn't cost them more.
High end places don't need to pay you more themselves to attract the best talent. There are only so many places in a given area where you can pull in 200-500 dollar nights. If you suck, they will fire you comb through the stack of resumes they have at any given time to find someone who seems likely to not suck.
/s