The reality is it nets them more tickets than they would normally receive. If a person wants to dispute the ticket, the officer will probably give them that opportunity. Don't ask the officer for proof . Demanding to see the officer's radar will pretty much net you a ticket every time. Besides, in many jurisdictions, he or she is not required to show you proof.
Proof comes later, in court.
They may choose to show it to you if you arrogantly demand it. Then you WILL be receiving a ticket. Don't snivel . If the officer sees you whining, you're ass is sunk. Cops hate wussies who cry over minor things.