Not just things like sexual harassment issues, there are plenty of reasons why internal communications and activity might not look great for the company if it came to a lawsuit. Just ask Cox Communications about how their abuse team's talk about the DMCA went for them. Now it won't just be overly candid email being scrutinized, but what websites the employees visit, what posts they liked, their chats, even their workflow. Why keep all that ammo around to be used against you?