How could a robust decentralised file system be useful?

Would you use one if one was available?

If so, to what use (storing, sharing, building apps on top of it, ...)?

If not, are there some specific reasons like difficulty to set up, legal, you already use one, or other?

I'm making one and it is fully functional but adoption is not here yet so I'm trying to figure out why.

Cheers

Edit: I'm referring to a decentralised online storage, accessible from anywhere.