Are you saying servers keep 90% of what you pay? Tip and otherwise? What country? How do you know? How could a business possibly operate in this reality?
Tax fraud, essentially.
E.g. you go to the Minnesota State Fair, merchants may offer to not charge sales tax if you pay cash. It is shockingly brazen sometimes.
> How could a business possibly operate in this reality?
Extremely lax enforcement on the part of the specific US state's department of revenue
I hand the cash to the cashier and they respond with "thank you, have a nice evening", while eventually handing me a printout of my order from their tables organiser software, instead of the legally required fiscal receipt.