Ever since I started playing guitar back as a teen, I realized pretty quickly that studio cuts (which is what we all heard on the radio) didn't always reflect a group's/musician's ability. Re-dubbing, mixing, editing, etc., can make some folks sound much better than they really are. You give me a tune I know well from the radio(studio version) and then do it live---There is the real measure of talent. The true artists can normally make it sound better live-oftentimes, much better--and that's when I give them the true credit they're due.
And like you, why would anyone want to hear/see a live performance that is virtually identical to the studio version? You could save a bunch of money and sit at home to hear the same thing. I want something different than studio--and almost always I'm rewarded with a much, much better version. I've only hear a couple of groups that were actually worse live than in studio. Not always their fault....case in point--ZZ Top. Saw them first time back in early 70's. Ended up seeing them several times throughout the 70s as well. Don't get me wrong, I enjoyed them each time.....BUT, when you only have 1 guitar, 1 bass, and a drummer....live simply cannot be as good as the studio version where they had some serious mixing & dubbing to get the final sound we all hear on the radio. Billy Gibbons plays lead guitar & some rhythm guitar on the studio tracks. Impossible to do it live with only 2 hands and one guitar. Some may disagree with me but I just find ZZ Top isn't nearly as good live as they are in studio. There are other examples too, but they are always the first that come to mind.
