Because the primary reader of a car’s identity is still visual, be it by eye or by camera. Swapping out every plate camera (arguments against scanners notwithstanding) and making it impossible for humans to read plates sounds very destructive at this time.

Anecdotal inconvenience: Teslas have a high rate of vanity plates in my area. I suspect it’s because they park in the same places and owners can’t tell them apart with 2 common models (3 and X) and 4 total colors (white, red, blue, black). Holding the fob is not something people do with touch/proximity unlock