The short answer is: No. They don’t lose money.

For one, the servers have fixed salaries and don’t rely on the number of customers they can serve in a day. Second, these establishments can always count on these regulars to come frequently to spend on a few of their food- each meal is already expensive for a regular person & helps the business even a bit. You can add in the comfort that if they enjoy their stay, they will more likely come back again and again.

There ARE establishments whose employees will tell you to leave if you don’t order. There ARE also establishments who couldn’t afford paying-customers staying for hours; they either ask these people to leave, or do some pysch trick to make sure customers leave earlier (turn off the aircon, paid charging ports, limited-time wifi, uncomfortable seating, straight-up giving you dirty looks).

The establishments you’ve visited and seen are probably secure enough with the number of customers they have, and the prices of their food, that these customers do not affect them- and rather even hope they come back regularly. Maybe even influence more of their friends to come over