BTW - bands and entertainers don't sell tickets to their own shows ... promoters (like Live Nation) sell those tickets, and "own" the actual show(s) from a business perspective.
A lot of folks don't realize that a purchased ticket is a 100% legal contract between the seller and the buyer.
As with any contract, both parties have to agree completely with each other in order for that contract to be valid, at which time both parties "sign off" on the contract (as a ticket buyer, you pay your money and take the ticket into your metaphorical hand).
If a promoter (like Live Nation) requires vaccination proof as part of their contract, but the spectator doesn't want to offer that proof ... then the contract is not fulfilled, you don't get a ticket, and you are unable to attend the event in question.
If you're unvaccinated, and vociferously complaining about not being permitted to attend your favourite artists concert ... nobody cares. You made a personal choice not to fulfil your part of the contract, and thus you are 100% responsible for whatever outcome transpires.