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.
I can do both just as easily. It really depends on if I’m going to be using the trunk or not. Believe it or not it’s actually illegal to back in some states. Cops are supposed to be able to see your license plate at a glance.