The reason people pay to store junk is they get attached to the junk. Then they’re homeless for a bit, just staying on someone’s couch. They need storage then. Then they get themselves an apartment but it’s such a pain to move all their stuff or they don’t have a car so they put it off.
Then their money gets tight, and they can’t afford the storage unit. But also can’t afford to empty it. They miss a payment or two, and a lock gets put on the unit. You can’t empty your unit when you’re behind on the bill. You have to settle up before you can empty it. So the monthly fees keep accruing and eventually they have the right to sell the unit.
You’re not allowed to participate in that auction (because then you could just get your stuff).
Storage places are allowed to use your stuff as collateral, so the stuff ends up for sale any time anyone can’t afford to keep their stuff. And most people’s stuff is junk so that’s why people spend hundreds to store it.
I lost all my junk in the above way, and it was a blessing. But at no point would I have consented to lose my junk, including at the start when the choice as toss all my junk in the trash, or pay hundreds to store it.