Exactly. That's also why they ask "Do you know how fast you were going?". It's less burden on them to provide calibration charts, etc. in court. Also, the only good answer to "you don't have anything illegal in here you don't want me to find, do you?" is "you do not have my consent to search the vehicle, and if you're going to search it anyway I would like your supervising officer to be present".
Depending on the country they do have the right to ask you to show them first aid kit, fire extinguisher and spare tire. Since they are usually hold in the trunk of the car, and the tire on the bottom this is as a good as a search.
