Does Your State Allow Year-of-Manufacture Plates?
When FL went away from the "1w 1234" format (with a smaller "w") it was ABC 123.
Now it's more letters than numbers but still 6 characters, although you can get 7 on a vanity.
I think because they have literally hundreds of specialty plates with different 5 and 6 digit patterns, that has eased the requirement for more digits on the standard plates.