Because they need both an ICE and battery powered engine it's a more complex & expensive solution than picking one or the other. Not only expensive in dollars but car weight, storage room, maintenance, and so on.
It's okay as an intermediate step but all electric is much better long term.
There are cases where hybrids remove complexity because they can be designed to operate either without transmissions, or with substantially more simple transmissions. Hybrids are cheaper than EVs since a good chunk of expensive batteries can be off-set by an ICE.
Hybrids are probably the end-game for any forms of transportation that require operation for a long period of time. A dump truck, for example, could have its 12L, 400hp diesel engine replaced with a 1L, 60hp engine that charges the batteries that drive the electric motors. Since the auxiliary engine only needs to be able to provide just enough juice for cruising, it can be made much smaller.
> There are cases where hybrids remove complexity because they can be designed to operate either without transmissions, or with substantially more simple transmissions.
This is how the LEVC taxis work in London; a 30kWh battery, charged by a 1.5L 3cyl petrol engine. Although in this case the kerb weight is about 200-300kg more than the previous (diesel) black cabs.
> It's okay as an intermediate step but all electric is much better long term.
Sure, but given the long term might be longer than the average consumer holds onto a new car, there's a lot of value in a good intermediate solution.
The average person drives less than 30 miles a day. Building a 360 mile EV battery just to handle long-tail events seems very wasteful.
Given that Lithium battery production is largely the bottleneck to full electrification, you could use the batteries from 1 Tesla and make 6 plug-in hybrids from them. And then get pretty close to 6x-ing the amount of carbon saved.
"it's a more complex & expensive solution than picking one or the other."
Not for NMC batteries, which continue to go up in price (so much for the downward EV battery price trend EV promoters promised would materialize with the economies of scale).
And LFP batteries don't have the necessary performance characteristics for high load applications.
It's okay as an intermediate step but all electric is much better long term.