Yes, it's wildly inefficient to use a vehicle with a 5000 lb payload capacity to make a special trip to pick up a gallon of milk. The guys I know with these things either use the other car (if they have one) or shop on the way home to avoid making a special trip. They work hard and aren't dumb, they don't want to waste money.
Also, at some point, driving an inefficient vehicle you have is still cheaper than maintaining another vehicle. And, TBH, the new pickups aren't that bad on fuel compared to the older ones.
I generally don't drive my truck (good for towing about 12-13k lbs, if not a big more) unless I'm hauling something heavy or large (big trailer, plywood, etc). We've got a smaller, more efficient car that my wife and daughter use. But, there are times when I'll take my truck with just me to get somewhere (dental appointment if I don't feel like riding a motorcycle after a filling, or if it's just downright crappy out, etc). It's not a common case, but the extra cost from that doesn't nearly pay for yet another vehicle.
My issue with the urbane EV driving set is when they condescendingly look down on pickup truck drivers en route to the airport to jet around the world for pleasure, burning massive amounts of hydrocarbons in the process. Whereas the truck guys I know will typically use their trucks to camp at nearby lakes for their R&R.
Or this forum... the reflexive "All personally owned trucks are evil!" thing is pretty well old. Yes, some people can get away with a minivan, or a trailer, but depending on the use cases, that doesn't cover everything. And the number of times on this forum I've seen people bragging about loading a vehicle well beyond rated payload is concerning...
A good time is camping on the lake for a weekend. Or up in the mountains. Take a good book, some beer, head up to somewhere you won't see other people if you don't want to, and hang out for the weekend. Hike around the area while you're there.