Restaurants and Pubs and even Airlines that allow all in, rather than only allowing those with a vaccination certificate in, will lose far more custom because a good proportions of the 80% who have had a vaccine will probably bypass those businesses...by exercising their free choice.
We have no idea of knowing until it happens but I think completely the opposite. I think the amount of people who will only choose the vaccines only business will actually be tiny especially if it means making a change from their regular pubs or suppliers and thats before we bring price into the equation.
Heres a real world example with hypothetical vaccine rules applied
Ryanair flights from Manchester to Dublin are £33 and allow anyone to fly
Aer Lingus are £74 and only allow the vaccinated
Do you really think Aer Lingus will get loads of Ryanairs customers?
Then take into account the fact that people whove had the vaccine should be immune to the virus, why would someone whos immune to the virus pay an extra £41 to sit with other immune people when they cant catch the virus anyway.
Similarly with pubs:
Pub A serves a fine selection of real ales and decent lagers and allows anyone in
Pub B only servers shit flat Carling to the vaccinated
If Id had a vaccine there would be no way Id be drinking the Carling as I could just go in the other pub and drink good drinks with people who may or may not have a virus that I was immune to anyway.
So basically the price and the quality of the products on offer would be a much bigger driver in making me decide where to go to drink or shop or fly.
You could argue that the vaccine only places could then compete on price and quality too but then they have the extra overheads of staff training, wasting time and man power checking peoples certs etc so probably wouldn't be able to compete on price as they would have bigger overheads