Not always true. Officers discretion. I've known 2 people who hadn't ever done anything in their lives that were asked to step out before. (No not me) Just comply without talking. If asked if they can search you say I don't consent to any searches of my person of property and I chose to remain silent and not answer any questions without my lawyer present.If you are being asked out of the vehicle - you're already in some pretty good trouble and the likely next question will be are there any weapons or drugs in the car? To which you can either answer or not answer. A non answer will get the passenger out quickly as well.
if your passenger was drunk, when you get out can they be charged with DUI since they are the only ones in the car? I think similar logic applies.
any good cop will do what he needs and let you go. A cop with an chip on his shoulder will hassle you and maybe even get a dog to come out. Stay calm an let them waste their time.