Humans constantly scan their environment to build a mental model of what's around them. And the harder a scene is to parse, the less energy you have left for conscious thoughts. A cluttered room is literally exhausting.

 
 

As food got cheaper (or we got richer; they're indistinguishable) eating too much started to be a bigger danger than eating too little. We've now reached that point with stuff.

 
 

If you don't have any immediate use for stuff you probably never will.

 
 

Stuff used to be valuable, and now it's not.