Drive around Kansas City sometime, particularly on the Missouri side. Tons of temporary paper license plates that are a year past expiration. Any member of law enforcement could pull the person over and enforce a penalty for it.
They just... don't. I don't know exactly why that is. Are they afraid that doing so opens them up to the chance of being shot or engaging in a high-speed pursuit? The former definitely happened in North Kansas City a few years ago (not to be confused with KC North) but having a massive network of cameras tracking license plates and how they move across town doesn't help. At the end of the day, you have to send someone a fine, and if they don't pay it and don't show up for court, you are again faced with having a police officer try to interact with them one-on-one, this time to enforce a bench warrant for their arrest.
In the meantime, you now have an absolutely massive data set of citizen movements being collected without a warrant by an increasingly authoritarian American government.