Very much this. Lithium batteries are the best battery we’ve got (at manufacturing scale) so far in terms of energy storage density, but the best we’ve got isn’t very good.

Gasoline has an energy storage density of around 13 MJ/kg. That’s a ton of energy, so much so that a vehicle can waste most of it generating so much heat that we have to bolt on a cooling system (with the associated weight) and still have enough to go highway speeds for hundreds of miles on a quantity of fuel weighing less than one of the passengers.

Toyota loves hydrogen because it’s got a storage density slightly higher than gasoline. Hydrogen has some serious volume and storage issues, but the density is there.

Contrast that with lithium ion batteries at ~0.7 MJ/kg (for the really good ones, which usually aren’t used in cars). Less waste heat, to be sure, but the bulk of the vehicles weight, the main factor in speed and travel distance, is the insane amount of material necessary to store the “fuel”.

Electric motors are far more efficient than ICE, but we need orders-of-magnitude improvements in battery storage density before EV can really take advantage of the greater efficiency. Until then manufacturers don’t have a choice, EV will be heavy and thus expensive.