Have you ever noticed how inconsiderate and stupid people can become when they park their cars? It's as if their brain turns off and they forget that other people exist. They find themselves a parking spot, and no matter how tight the fit, they take it. Conveniently for them, they can squeeze in nice and tight on their passenger side, since they'll be getting out of the car through the driver's door.

Inconveniently for me, I need to get in and out of my driver's side door too. But your car is too close for me to even squeeze in.
I don't really car about my car. It's full of baby stuff, scratches, and the odd rust spot. So next time you park too close to me, I'm going to nail the side of your car with my car door. Then I'll drive away.

What about the jackasses who park right up close behind and in front of you? It's bad enough that I had to parallel park my way into a spot, but for you to come afterwards and block me in is completely inconsiderate and rude.
Did you forget that you live in a city with other people? Apparently so.
So the next time you park your car, stop and think - am I going to be an asshole and block the other guy in? Parking is pretty simple. You're probably driving slowly, so you've got time to make the right decision.