Stickers are _way_ cheaper than plates, and can very easily be changed as the program changes.
Also, just having stickers avoids the confusion of having two different types of vanity plate.
Easier for whom?
The EV/alt fuel plates in AZ and CO have been very well-received.
I've now got a set of white and a set of red stickers (go figure - no way that should have happened, but it did - with the correct paperwork for each, even) in my car. Not *on* my car, I should note. Although once in a great while I'll put one small sticker on the rear adjacent the license plate, but then it comes off after journeying through the 2 high-enforcement areas hereabouts. The joys of cling vinyl, which has worked surprisingly well. I've also got a roll of magnetic tape, but haven't needed it.
The entire program is offensive. If they had a designated plate, I'd happily get one/them and pay whatever for it/them. Meanwhile, in 3 years or less, sticker cost has tripled ($8 --> $22) and will continue to get juiced as a revenue source.
It's not like Teslas will grow a tailpipe anytime soon. Nor is there a traffic cop on the continent who doesn't know what the ass end of a Tesla looks like.
See offensive above - it's a revenue grab, plain and simple. Both on the streets and on highways - enforcing stickers instead of the type of car is not only lazy, but again, offensive. Rather similar to writing tickets for 1 mph over the speed limit. See lazy, opportunistic, and lazy again. Magically, Hermosa Beach manages to offer free parking for EVs without the silly/lazy requirement for stickers of any color; so either their 6 meter readers/coin collectors/parking enforcement minions are vastly more competent than their Santa Monica brethren/sistren or perhaps they're just less craven/governed by less craven statutes?
I'm surprised they don't bring back paying cash on the side of the road else getting hauled off to see the judge. For an additional charge, of course. Ah, the good ol' days in, for example, certain counties in the Deep South.