If something goes at linear velocity, there is no force and the object can't tell if it's moving or not. It might as well be the whole ambient space is moving (relative to the object) - it makes no difference.
But if the object is rotating (e.g. a spaceship) in vacuum it stays in this rotational motion (due to conservation of rotational momentum), but there is still centrifugal force on the object (e.g. on a person in the rotating spaceship). Why isn't this the same as in linear movement? Shouldn't it be the same if the ambient space is rotating or the spaceship is rotating? But in one case there is a force but in the other case there is no force?
If you'd be put in an infinite vacuum and would accelerate, when you stop the acceleration, you might as well be stationary. But if you would apply angular acceleration and stop the acceleration, would you still feel the centrifugal force?