One answer is also that people are fat. Americans are friggin huge (40% of adults are obese), with Europeans lagging in size behind US "growth" by 15-20 years.

You are incorrect that SUVS aren't bigger. They are. We are trading our BMW 328 for a BMW X3 because it is about 20 cm longer and a lot more storage behind the back seats (#40kgHuskiesTakeALotOfSpace).

We took a test drive to make sure the larger vehicle would fit fine in our parking space in our garage. Not everyone does that, which does support your "stupid" theory.

I used to live in Houston and drive a Suzuki Swift. I like small cars. When we had two cars, I liked have a small second car (e.g. Mini). Driving my Swift in Houston I basically looked at the bumpers of the trucks all over Texas.

It is dangerous not to be able to see through the windows of the vehicle in front of you. Therefore, having a higher vehicle when most others do is also a safety issue.

I think every country should have a legal standard for a parking space. Some countries do. Vehicles wider or longer than a standard parking space should pay a substation and non-linear (e.g. a car 10% larger would pay more than double more than car 5% larger) yearly fee.