Contrary to what OP said deleting content will make devs have even less time. You don't need to QA old content, and I really doubt SE even looks at it, but if you remove anything you absolutely need to make sure nothing references it and that there's no crashes or other undefined behavior because of deletion of some content. That is some real work and if any crashes happen because of it... well I wouldn't want to be the guy debugging it and I feel sorry for the guy who would have to.
Funfact: Nothing has ever been deleted from the game files. Even the old Tomestones are still there even though the oldest ones were phased out soon a decade ago. They are inaccessible but not removed.

Also this argument

Quote Originally Posted by Venandi View Post
They don't have to do QA on it and by deleting it, it gives them more memory to make new content.
The biggest memory hogger in anything is the graphics and the server side doesn't have them because why would it need them. It likely just has some binaries and scripts and the size of them is probably very minimal if you look at what's taking space. If you are concerned about memory point your finger at player data and I'm sure there's not much you can do to the size of that.