Backing up out of a parking space isn't hard. But it is not as safe as pulling forward out of a parking space.
When you back out of a parking space, there could be pedestrians that you can't see, or small children darting about or a stray grocery cart or the like. If you drive a small car and end up having to back out of a space with much larger cars on both sides, it is very, very difficult to see if there is anyone walking down the aisle or any other cars are in motion. You have a very limited field of vision when backing out of the tunnel formed by mini-vans on both sides.
If you back into the parking spot, it is a tad more difficult because you need to be careful that you don't hit the cars on either side, but there is less of a chance that someone will be walking behind the car.
That's why some of us prefer spaces where we can pull through two spaces. All the ease and convenience of pulling forward in to a parking spot, plus the safety advantage of pulling forward out of the parking spot. You can see where you are going and are much less likely to hit someone or something.
The chief problem with backing into a space is that other drivers frequently don't like waiting for you to back in slowly and get impatient.