I have a pickup so my opinion is a bit biased, but when backing into a spot you have clear lines of sight on the road in front and behind you, as well as pedestrians who might be walking along parked cars. All you really need to worry about is where your back bumper is in relation to the cars you’re parking between, the rest you’ll see in your peripheral vision. When backing out of a spot you’ve taken too much time getting into your car so you don’t know where traffic/pedestrians are coming from and can’t see them until the rear 1/4-1/3 of your car is already backed into the road/lot