Most people do not carry their registration with them. Just because we ask, doesn't mean we get it.
Around here, nothing happens if you don't have it. To tell you the truth, the reason I ask for it, is to get them to open the glove box, you would be surprised what falls out sometimes.
A friend of mine pulled a couple over one time for speeding and the female was in the driver's seat and the male was in the passengers. He asked the female driver for proof of insurance. She said she didn't have the card with her. Her husband got this confused look on his face and said,"What are you talking about? It's right here....." as he opened the glove box a bag of marijuana fell out. He had no idea she was smoking it and they got a divorce a few months later.