I can understand why you might think it never happens if you are completely ignorant of the facts on the ground but nevertheless familiar with the criminal and civil sanctions involved. It's about lack of enforcement.
https://www.phillyemploymentlawyer.com/wage-theft-epidemic-r...
https://www.epi.org/publication/employers-steal-billions-fro...
https://www.restaurant-hospitality.com/legal/la-restaurant-p...
https://www.eater.com/2018/9/25/17886990/how-restaurants-ste...
Obviously, none of these are scientific studies but I don't know if there are any done in the industry.
What I'm trying to point out is: Wage theft of all types happens all the time and I've known people too poor to risk losing their job who suffered under this issue. I'm sure it doesn't happen often -at scale-, in chain restaurants with big corporate backing but in an industry where most close after their first year and the workers are frequently undocumented or transient. It happens.
Not really worth it. I'm not saying it doesn't happen, but the calculus is so bad that it's extremely rare to happen at scale. Especially if there's a digital trail run by a third party...