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.
The steering axle is in the front. So if you back into a parking space, you turn around your back axle. This makes the alignment considerably easier, especially for tight parking spaces or crowded parking lots. If you wanted to park front first in that situation, you would have to correct several times because the turning radius is too big to get the car straight in front of the spot in one swoop.
This is exacerbated the longer your vehicle is. It is impossible to turn wide enough with my pickup truck to park forward because the front end swings too much. The more efficient car I take on normal commuting doesn't have this issue.