To me, it seems objectively easier to pull into a parking space forward and then back out of the space when you are ready to leave. You don’t have to line up with the lines while driving backwards, and it’s easier to keep from hitting other cars as well. So why back in? To me, the only advantage I can think of is that you can get out quicker, technically.
Edit: I do not need driving instruction, just wondered why. The reasoning.
Once you know the proper method, it’s easy and efficient. Knowing the proper method is requested to get a licence so many people don’t forget.
A big bonus is that you see where you go when leaving. So if a car comes on the street you see it.
Finally many companies have a back parking mandatory as it’s safer in case of emergency evacuation. Not an issue in a supermarket but definitely a thing on a chemical factory