It's also a big inconvenience for your customers. They aren't able to update to the latest version and would always rely on someone being online in order to update their server.
There's also the downside; you can't really announce that customers' servers will go offline. You might know what date updates usually (read usually) happen, but not the exact time.
If the client is in the middle of a game (because they haven't shut down their game and let the update happen client-side), you're quickly gonna earn yourself a big pile of angry customers - all because you want to save some space. I can't find any solution for this without it having a major downside.
Plus, disk space doesn't cost anything today.