If a provider has open capacity on their storage device, why would they supply space to MedAI vs Sia Coin, Filecoin or other blockchain storage providers?

Typically medical grade storage can provide higher reimbursement rates due to the introduction of enterprise customers paying for storage. This network effect benefits all users.

We see this effect in non-blockchain storage apps such as Box.com and Dropbox that have both tried to develop healthcare specific products and failed.