Right but what's the point? If the belt is on very loose, you give your body a chance to gain momentum, which will be redirected when the seat belt catches you, which would lead to serious injury.
The belt doesn't need to be on tight, but it should be relatively snug.
It's just one of those things that is trivial to do, with a very, very low probability to save you from injury, but costs nothing, so why not...
