What's with the "wine-dance"?

I'm frequently told by Bloom diners what a relief it is to be served wine in a glass, and thus be able to skip the whole open-bottle-gurgle-and-discuss dance. I kind of agree, over-pompous sommeliers tend to make it more of an event than it actually is. So what's the dance actually for?
Well, when you order from a wine list, the showing of the bottle has nothing to do (really) with looking at the nice artwork on the label. All the waiter wants you to do is have a look at what the label says: is it the same vintage and vineyard as was listed on the wine list? If you don't want to comment you don't have to. Just nod or shake your head. We'll get the message.
Then there's the pouring of a sample to taste. You don't have to expound on the bouquet or gargle the wine at the back of your throat, the tasting is merely to ensure that the wine isn't corked or otherwise flawed.
But as I said, at Bloom we take care of all of that for you. Still, it's not like you can't get a different wine if you don't like the one we just served. But of course, it makes things easier if you'd be so kind as to tell us that you don't drink red wine at the start of the evening (we're only humble wine waiters, with no claims to clairvoyance).