That may be, but it is legal. Cops can now do it instantly from inside their car on a computer without calling it in. If a cop is behind you at a traffic light you can be sure they ran your plate.
That is the only reason to even require license plates, so cops can check them, and they do that constantly.
That doesn’t make it right.And people like you that advocate that it’s okay to do so is why our freedoms are diminishing more and more every day. Running a plate is no different than a cop stopping a guy walking down the sidewalk minding his own business and demanding his ID just because he looks funny.