I don't disagree with reusing the old cards. Our bank cards are for several years and on the green side it saves more plastic being used (however small the amount.)
However it shouldn't be difficult (even with changes) to re-allocate a card to a new seat / ticket option, after all if you don't pay your membership renewal at Gwynnes your key stops working at the door, when you pay it it works again and that is much simpler tech with a much smaller operation.
Even if QR codes are programmed to mean an exact thing (person+seat+ticket option) it should be able to be re-assignedd like you can reassign any barcode to anything pretty simply. If it can't be reassigned that way like barcodes then its another case of new tech "being beat" by old tech (IMO.)
@StrangelyBrown The betamax option above is nonsensical. You could use that as in choosing not to have a video player or not. I don't choose to have a dumbphone over a smartphone. I would choose not to have a mobile at all but the wife insists it is necessary "for emergencies."
Betamax vs VHS is like saying Netflix vs Sky vs Prime vs Now or even all of them and I choose none of them. Or choosing dial up vs 10mb BB vs 300mb BB and I choose the 300mb. I could equally choose none of them. Those are choices.
The road to the smartphone being your only access to everything (which is quite possible looking at how things are going) removes that choice and forces people to spend their own money whether they like it or not to access things. Ther will be no choice.