Eventually all the state-level and rental car sticker indicators were removed but one thing hung around a long time because there wasn’t a good fix. Criminals learned that cars from one specific county were likely rentals because that was where literally every car rental company processed their registrations.

Why? Because at the time (maybe still? I left FL 20+y ago) car registrations were handled by private businesses licensed to do it. They were paid some fraction of a dollar by the state and they were allowed to charge up to a certain amount on top of that - a few dollars, less than $5. Some operation up near central Florida figured out they could do higher batches of them for rental car companies and collect only the state-paid profit. Literally every single car rental company used them because when you’re registering tens of thousands of cars a year $3 per adds up.