The major issues to this is hacking but I don't think that is the only. These files or data are stored for easy accessibility, recoverability, security and leveraging the storage space available on these servers. Now, shutting it down kind of takes all that away and one dumb enough to store there private keys or seed phrase online with hopes to recover and import wallet in the invent of a crash might have just lost everything.
If hacking makes you lose everything and shutting down a service has the same effect, then technically, we could say they are the same thing. Offer the same risk, just different means!