Because you need the files to do proof of proof-of-storage and get your coins (back).
But as the OP said there's currently no proof-of-will-to-distribute-storage so you can save money by just sending the proof-of-storages to the network and never actually provide bandwidth for the distribution of the stored data.
But as the OP said there's currently no proof-of-will-to-distribute-storage so you can save money by just sending the proof-of-storages to the network and never actually provide bandwidth for the distribution of the stored data.