In my city, you can rent a truck for the day for about $50 (including a decent amount of miles). I know because I do this regularly. I'd be surprised if such an option isn't available in your city as well.
The cheap rentals in my city are at the airport and that makes it a pain to use them. They're not really cheap if I ascribe a sufficiently high value to my time. The ones close to me often have limited inventory and don't have a pickup truck right now.
Even at the airport, it looks like a pickup truck is $200 for the weekend. And honestly going to the airport is enough of a pain that I'm less likely to do things that require a truck as a result.
If I owned a pickup truck and kept it in a garage by my place then I would be far more likely to make last minute decisions to go camping or yard sale shopping or whatever.
You don't need a pickup truck to go camping (they're actually not terribly useful for that) or yard sale shopping. Like seriously it's https://van.life not truck life.
That's a good call on vans though. A cargo van might be a good idea for legitimate well maintained campgrounds.
In my area, renting any vehicle at the airport is more expensive than the same vehicle at other locations.
You and every other SUV driver share this dream. We all know that last minute outdoorsy fantasy is not gonna happen. And are you buying the entire yard at the yard sale?