Because in many restaurants, if the person does not pay (dine and dash), the waiter is left with the responsibility to pay the bill.
I went to a restaurant several states away. A couple weeks later I looked in my wallet and realized that I brought home the signed receipt. I called and was told that happens often. They just process it with no tip. I felt bad and mailed a check to the waitress. Wasn’t $1000 though. I think it was 30%.
Then a couple weeks ago, I was again out of state and forgot to grab my credit card. When I called a couple days later, they still had it and mailed it to me.