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.
When I am entering a space I have 360° visibility. I see all, I know all. I can therefore make a calm and practiced motion while being fully aware of my surroundings as I park.
When I am leaving the space my view is inherently restricted. If I am pointing out I can see to both sides, see oncoming and same side traffic, see pedestrians, and see even more as I pull out of the spot.
If I am pulling out in reverse I can see far less. I have a very twisty neck so I can see behind me (180°) plus another maybe 40°, leaving me with an 80° view, but it is from the opposite end of the car space so it is narrowed. As I pull out I see more, but the whole time it is more narrow. I can’t see the rear of vehicle and I certainly can’t see far to either side of the vehicle at the road level.
So I think the key is thinking about your worst visibility. I think the overall visibility is better when I reverse in to the space and drive straight out when compared with driving directly in and reversing out. I think I can see small people and kids better over the bonnet of the car rather than out the rear window and I think I can react better to the situation when I am reversing in than when I am reversing out.