All you can eat buffet TIPPING?

Pretense im in the UK where tipping isnt the norm

In the last few months i had an experience where i went on a date to an all you can eat buffet and we got sat down, the waiter asked us if we wanted drinks (we ordered 2 glasses of wine) and she left. I didnt see her again the entire 2 hours we were there. Not once
And thats okay because its a buffet, you get up, grab food, sit down, repeat you dont need a waiter.

At the end i asked for the bill and all, it was the same price we booked it for whatever, then there was a tip option and i got stared down like never before, obviously i pressed no, she didnt appear i dont know if shes good or not how tf am i meant to know, and you dont usually tip anyway here.

Despite that when i pressed no, she scoffed at me like i just spat in her face and insulted her dead mother.

Can someone explain?