Wouldn't there be a selection bias, as trucks in parking garages are much less likely to be doing hauling /towing tasks?

Half of them sticking out into the roadway blocking half the lane. What an entitlement.

I counted 50 sedans with empty seats in the parking garage downtown this morning.

So? You saw them for one subset of what they are doing. Perhaps the most common one, but still just a subset.

But a lot of people buy trucks so they can tow and carry stuff when they need to, not because they're doing it all the time.

Downvote all you want, the sales numbers speak for themselves.