Historically gas was a reasonable proxy for road use, but that is going to be increasingly untrue. It's reasonable to see EVs as a tax dodge against road use taxation that can primarily be taken advantage of by the well-off, but in AZ it's $100-$200 a year.
Either give EVs a 1¢/mile use tax or give everyone the tax and remove the gas tax, or drop them both and become more efficient ;-).
Registration in Michigan for a Model 3 is over $500 a year and used to be closer to $700.
If you assume 12,000 miles a year that's only $720 total since the 3's release at 1 cent a mile.
This is true for electric or hybrid, but in general, heavier ICE vehicles will have lower economy which means they buy more fuel and pay more fuel taxes. In many states trucks cost more to register too. So it's probably pretty close to proportional.
Nobody's forcing anybody to buy the giant ones, though, so a few good choices existing is enough that "car seats" isn't a reason on its own to buy an SUV.
It just seems super wasteful to me the number of vehicle-miles that are driven in the suburbs by enormous and medium-sized ("Tall Hatchback Camry") SUVs with a single driver carrying a couple bags of groceries. Most of the time, most commuters and even people with up to 2 small children ought to be perfectly fine driving a 4-door compact, which is substantially more fuel-efficient and lighter than even the midsize SUVs. But the incentives don't exist to make people consider that. They figure, "Oh well, I'll spend $25 extra on gas each month but it's worth it so that I can transport lumber once a year."
This is a categorically untrue myth. Lots of car seats are stupidly wide thrones, but there is no reason you have to buy those ridiculous things. Diono makes a full line of car seats which fit 3-across in any midsize car. They're even cheaper than a lot of seats from the biggest brands, starting under $200. [1]
People are buying SUVs because they want them and because we've made it attractive to do so:
* Externalize excess road wear costs onto all taxpayers due to gas tax
* Overall trends contributed to pathetic selection of good sedans
* Finally, Reasonable fears that since "everyone else" is driving 3-ton monstrosities, perhaps they won't be safe in a car 5 feet shorter than the truck that hits them.
It won't be easy to reverse any of this, since the only lever is to replace gas tax with a fair road tax like this Norway one -- the rest of them are functions of the trend. Sadly, anything that raises taxes on a majority of Americans (those who drive big SUV things) would be political suicide.
[1] https://store.diono.com/radian-3r/ (No affiliation with them, though I've purchased 4 of these so far personally.)