Because the only effort ticket buyer should put into a purchase is making the payment?
If I was going to spend $200 to see an 88 year old performer, sorry, I would most definitely be looking into his current history. Which is so easy its ridiculous but why make the effort when you can just wing it and what you could've anticipated catches you off guard?
There are all kinds of musicians. Some put no more effort in than to get up to jamming with a friend levels. Others spend their lives on stage. Some even die there. Apparently BB put on a good show following this. Should he still bill it as more talk than playing if that's not what he did that time? Should he have quit right before this? Should he quit now?
If anyone's money is so important that an unexpected show leaves them as butthurt as many seem yet so unimportant they can't be bothered to check on recent performance beforehand...
How important is it, really?
What a quandary.
I've been to good and not so good shows. Never had a reaction like this thread. Because no one has to retire for me not to spend money on them (again).
People have gone so far as called this fraud.

. Heck, get a lawyer and sue him for breach of contract. I wonder if some folks ever step back and look at how they act from outside their personal confines. It ain't pretty.