It’s easier on your later self
It’s something that once you notice, you can’t unnotice. I could be wrong, but nine times out of ten, Japanese people reverse into their car park.
The theory goes, and remember it’s just a theory, that you’re going to have to reverse in sometime, so why not make it easier for yourself later? I.e. when you leave? If you have to leave in a hurry, say there’s an emergency, this way you’ll more easily be able to start driving again. It’s easier on your later self, in other words.