Yes, supply and demand on exchanges but who knows what more? If you want to pay your resaturant bill with Bitcoin you always need an intermediate because the transactions are way too slow for direct payments. So who knows what EOS will bring? Maybe you have an App on your phone that says: You have 54 dollar in EOS. And next you pay a bill somewhere and just see the price in dollars while it’s doing an EOS transactions on the blockchain.
Here’s the whitepaper for EOS-storage. I guess it won’t be that hard to use it, will probably look like some sort of dropbox if you want to store some files.