Why does buying a car from a dealership have to be such a huge ordeal?

It’s about time for me to buy my first car, and I’m finding that it takes so much effort on the customer’s part not to get ripped off. I just can’t believe the number of articles on the web about how to outsmart your aggressive salesperson. It sounds as if they’re giving advice on how to avoid getting mugged (are they wrong?). This is totally the opposite of what a shopping experience should be. Why isn’t there more consistent pricing on cars as to eliminate the need to negotiate? Why have car dealers earned a slimey reputation and why do they perpetuate it?