Google Drive

has all facilities like docs, spreadsheets, slides and can easily be shared

Files

convenience

I have "unlimited storage"

All your files, like all of them

There's no better way to store documents organization-wide. Especially since you've got the Google suite right there.

It's used to do everything

Because it's convenient for storing, managing, and using files on the go

Easy sharing and saving in storage, as well as the docs/sheets/collab.

Reliable, intuitive, and 15GB storage for free ain't bad! Is your data safe? Maybe not, but you can combine it with a service like Boxcryptor and you're all set.