Corsets aren't all bad but like anything, too much/all the time isn't good. There's certainly women who wouldn't have done it safely (after all, why slowly reduce the waist when you can try to go straight to as small as possible). If you wear it while eating, it's not gonna be comfortable and there's potential for some medical issues there. If corsets are done improperly, they can also affect breathing, etc.
Also you just know that no one at a ball is gonna wear it comfortably. Nah, they're gonna make it as tiny as possible to have an itty bitty waist.