Again you are assuming you have much more impact than what you, as an individual person, have.
You deciding to not spend £20 in a pub is going to make zero difference to that pub in reality.
On one occasion, true. That said, you would be surprised at how many places rely on a small number of regulars. If my local tried anything like this, and the four of us that go in a couple of times a week to watch the match and have a round each opted to go elsewhere, that works out at slightly more than 20 quid over the course of a year, and given said local is, right now with reduced capacity, nowhere near profitable, that would cause an issue