Because those files are server-side for a reason. If they were client-side, then players would be able to decrypt them and add things to their inventory that they didn't have before, and when the game syncs back up, they would have something they didn't earn.
tordr86b16_ESO wrote: »Do something else, like idk, go outside and feel the sun on your skin?
How about ZOS makes it possible that you can still do quest, collect mat, etc, when server is down, and sync back the data when the server is up?