Also depends on local law enforcement. In California, you are required to display both front and rear license plates, but probably 25% of cars don't have a front plate, never seem to get hassled over it. Not to mention all the beaters that have one or more (sometimes none working in the rear) lights, etc.
I take pride in making sure my car is in good working order, but so many look like they should be scrapped, cops don't care about that it seems.