Are you not sure why, or simply don't know? We don't know what CA EV rules and benefits exist. You are at a disadvantage in not knowing the history.
From about 2010-ish (if I recall correctly) until 2020, EV plates helped Law Enforcement and Parking enforcement to recognize what vehicles the state declared were allowed certain perks. The perks being an incentive to buy non-ICE vehicles. The category included BEVs and Hybrids. In those early years 99% of the people including LEO's didn't know what a Tesla was especially that it was an EV. Some of the perks were, free parking in city/state lots, free street parking. free parking at the airport lots (really big deal to the point of abuse), travel in HOV with 1 person in the vehicle.
The laws sunset on most of those but the fed regulation that allows us travel in HOV anytime. The EV tags precludes a ticket for HOV driving. In other words, if you don't have the EV tag, you are likely to get the HOV ticket if caught. Of course you can take the time to have it over turned, but having the EV tag is easier. Now they punish us for having an EV with not simple a "don't pay gas tax" fee, but an excessive charge above what equal gas tax would have been paid.
Even with the ups and downs of perks or penalties, many/most of us still carry the EV plate because we are proud to be driving not just an EV, but the best made. I'll simply assume you believe the same.