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 learned to drive in the US and always pulled into spaces. Since moving to the UK I almost always back in. The difference is I find it much easier to back into a tight spot (as basically all spots outside of the US are) and then drive out rather than the other way around. For whatever reason backing out of a tight spot is much much harder than backing into it.