Meh. Most people only ever use the front row of seating in their vehicle the overwhelming majority of the time. Pickups are just vehicles where the extra space is optimized for non-human cargo. The richer you are the more likely you are to buy enough vehicle for the most extreme case. If we all bought what we needed for the average case there would be a lot more subcompacts sold.

Right, which is why pickups should be taxed more than cars to internalize their externalities (lower fuel economy, more damage done to other vehicles in accidents). It’s not like it can’t be done (See: this article on Norway).

They are. Any gas tax is a tax on the fuel economy of the vehicle. If pickups get less MPG, they are taxed more on gas tax. Some US states base vehicle registration fees on the weight of the vehicle, which is another tax on heavier vehicles (like pickup trucks). More damage done in accidents is something the insurance companies would have to deal with, and if it's actually a problem you can guarantee those insurance companies have already factored it into the rates.

In at least some states, they are.

I regularly nearly exceed the load capacity of a 1/2 pickup. Some of them are road queens but some people actually use a truck for its intended purpose.

In which case a pickup truck is a superior solution over current EVs.