And I'll clarify that its not 'right' that peace officers do do it either.
The ACLU and a law professor have videos on YouTube telling you, "Do not talk to police."
http://www.youtube.com/watch?v=6wXkI4t7nuc
They make it clear, do not say a word. Do not identify yourself. Police can arrest you from something you say even though you are innocent of any crime. If you are talking to them and you fudge the truth and then you tell them something else which makes them realize that you have lied, they can arrest you. (By the way, police can lie to you, but you cannot lie to them. What a sorry system.) These are two really good videos even though I don't care one hoot for the ACLU. Tell the police you do not give consent to a search of your person or property. Unless they have a RAS they cannot legally search you. If you asked to get out of your car, roll up the windows completely and lock your car when you get out and put your keys in your pocket. They cannot legally take your keys without you voluntarily giving them up. Once you do you have waved your constitutional rights to a search. If they take them from you without reasonable cause and you have warned them you do not give consent to a search of your person or property, you can get a lawyer and sue them. They can search your car, however, if you give up your rights. You and your car better be clean from drugs, guns, or prescribed meds that you cannot show a prescription for if you ignorantly give up your rights. I will see if I can find those videos and post them here. They are well worth watching.
If I made an error on something said here, the films will clear it up.
Edit: As much drug use as there is in this country, if you buy a used car, you better do a good search that no drugs are still hidden away. If you get stopped and the police find any drugs...guess who is going to get busted? You may go to court and are found innocent...but you will have spent a lot of money to prove your innocence. Keep the police from searching your vehicle. Here's some advice to follow:
http://www.youtube.com/watch?v=yqMjMPlXzdA