It has been done to avoid someone drinking wine with "cork". The taste of the cork used to close the bottle can be transmitted and makes the wine taste quite bad.

Modern cork is no longer cork, but rather plastic. Then its show, in my opinion.

If you order an expensive bottle, lets say some Margaux usually no one expects you to accept and pay for a wine that doesnīt taste as it should. Most wine stores /whole sales have return policies for bad bottles, so that it doesnīt cost the restaurant anything. If its really expensive, it on your own risk!

Otherwise, if itīs a rather normal wine and you choose from a menu, it might be done to let you try the wine first before ordering a whole bottle or more.

And no, once a cork ends up inside a bottle of MR due to inexperience of the waiter, you donīt have to accept to drink and pay for some filtered, then poured into a decanter 1982 MR wine!

Generally, I think it has been the spiel so long, it will stay that way for ever.