My dad's and architect and the number of self storage units being built is astounding. We have theorized that it's 2 things, boomers had a shit ton of stuff and are dying / downsizing. When the younger generation is inheriting the things, they live mostly in smaller rental units ( home ownership is waayyyy down) so there's nowhere to put the things. It's all across the country too, so it's a massive shift of just stuff people can't fit. This is why I only buy from the used market these days, everything's so cheap!