You only think it's no big deal because you probably haven't considered several rounds in a row of Time Stands Still, Ancient Mountain Hammer, Death Mark, or any other strong maneuver. Let alone several rounds in a row of White Raven Tactics. It's a lot harder and a lot weaker for a multiclass martial adept readying a low-level maneuver with each of 2 or 3 martial adept classes.
Anyway, no, you cannot ready more than one copy of a maneuver at a time with any given class. You have no maneuver slots; they are not spells. You just choose a certain number of your maneuvers known and ready them. Only multiclass martial adepts can sort of do so, as described by StreamOfTheSky, by readying one copy of a maneuver with each martial adept class (assuming they know the maneuver separately for each class).