It's far cheaper to use a storage unit for a lot of this stuff I do routinely use than buying and selling a house just to get more storage space at home.
I'm not blind to the fact not everyone just stores junk they never use. I'm certain there's a percentage of stuff in mine that is probably better off sold or trashed. But until we stop changing decorations for the different seasons, stop a number of hobbies with bulky stuff, or move to a giant mansion I just don't have the space and could use a few more square feet of pure storage space.
Every square footage of every home costs $$$ to keep in your possession. I pay a mortgage. I pay insurance. I pay taxes. I pay maintenance costs. There were acquisition costs in the purchase of it, and there will be acquisition costs wherever I go next. Not one square inch of my home is "free".
Suddenly that simple answer isn't so simple when actually confronted with reality, unless you're willing to be homeless and just carry your possessions in your hands.
I have to regardless of a storage unit or in a closet in my house. That closet in my home and that shelf in my garage isn't free either.
So then it's just a question of owning anything at all or nothing, because it all has a life long recurring fee for the privilege of continuing to own it. And yes, my family finds value in decorating for holidays as a part of celebrating, remembering, and keeping traditions alive.
Sometimes people don't just want to live in the same IKEA box 365 days a year.
Are all these comments like yours coming from college students or what? If anything else, a storage unit is one of the most valuable things to pay for if you just moved out on your own.
It seems hard to imagine the sums involved becoming comparable to other amounts of money lit on fire to avoid fights with family though (i.e. home renovation, travel).