You're half right about the seats but seats that fit three across in a normal small SUV or sedan are a small share of what's available. I also think it's worth segmenting out SUVs now that everything has become an SUV. The Corolla Cross is an "SUV" but really compact. A RAV4 is an "SUV" and one of the most popular vehicles sold in the US but it's only slightly heavier than a Camry and gets about the same fuel economy (because it's basically a tall hatchback Camry). Even the next size up (Highlander) is about the same weight as a mini van (Sienna). Weight based tax seems like a good idea to me but I don't think "SUVs" are in general really the problem.
And fair point that SUVs aren't automatically enormous, nor automatically super harmful, except in how deadly their genre-defining high stance is to pedestrians and children.
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."
> seats that fit three across in a normal small SUV or sedan are a small share of what's available.
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.
