What I said was, "I'm not being a bitch, I'm being informative."
Other possible answers:
Because I can.
Because I'm tired/depressed/obsessed with parking spaces (more on that in another post that I'll link to later)/hungry/you fill in the blanks.
Because you parked wrong and didn't put up your handicapped sticker (and I did point out if a police car came by, the fine is $100 and it's their $100, not mine).
The situation: I was leaving Wal-Mart and someone parked straight in one of the sideways handicapped parking spaces they recently put in. I hate these spaces, but finally came to the understanding that there are a lot of people out there with their own carts or even wheelchairs that will benefit from the larger spaces. But you are supposed to drive right in, facing the store in this case. This guy parked parallel to the store. I've seen people park 2 cars that way in one space.
So I waited and when he got out, I told him how the parking space was supposed to be used. He said he didn't feel like parking that way. I looked at his license plate and where you're supposed to put a hanging sticker if you have one (rearview mirror) and didn't see any handicapped insignia, so I said, as a reminder, that he forgot to put it out.
I have forgotten that on occasion and when I realize it, I am always thankful I haven't gotten a ticket yet. I only use it when Mom is with me and is actually leaving the car to go into church or the store or wherever. If she's staying in the car, I park in a normal space.
So, after I reminded the driver about the handicapped sticker, the woman passenger said, "why are you being such a bitch?"
I'm sure if I think about it, I can come up with a few more answers.