It's beyond me in this day and age of ubiquitous information available at one's fingertips that anyone can walk into a dealership and NOT know what they want to buy (or at least have it narrowed down to one or two models and/or trim levels). You should do all your research BEFORE going to the dealership. The only point of going to the dealership should be to actually drive the car and confirm or refute what you already know about it.
Dealerships HATE informed customers because it basically removes the need for a salesperson. I don't WANT some smelly guy in a bad suit trying to tell me what I want. I already KNOW what I want. The only reason I'm even there is because I can't order one from the factory directly. I have my financing worked out with my credit union before I set foot in his doorway. The salesperson's total interaction with me ought to be "Here is a filled-out build sheet for the car I want along with all options I would like. Here is the price I'm willing to pay which ensures a modest profit for you and your dealership. I will not negotiate one penny above and beyond that, nor do I want to be sold on additional options or extras I have not already specified. Please locate the car in your database. If you have one on the lot that matches it, I'll take it today. If not, please have it delivered here and let me know when it arrives. Thank you. Goodbye."
Why in the hell can't we just ORDER these things from the factory??? Oh, right...car dealerships have local politicians blocking that sort of thing. Land of the free, home of the brave-but-not-so-brave-that-we-want-actual-competition.