Sure but you have a lot of options if you control your own emails that you don't have if someone else does. For instance, you can actually delete your emails, and know they are deleted (obviously I'm saying before any such case). The same option does not exist on the cloud.

(incidentally this is exactly why most corporations these days have a pretty short email retention policy, something like 3-6 months. As long as you delete the mails before a complaint, or at least before discovery is granted, there's nothing wrong with deleting them, even if it is to avoid them being used against you later. But there's other advantages too: it helps me get organized, and it prevents me from obsessing over things that have slipped so far down the priority list they'll never happen. Which is very soothing. Plus it breeds the good habit of not storing important things in your inbox)

I would like to point out that often the criticism is leveled that you'd only do this if you're guilty. Aside from that that is the "if you've got nothing to hide ..." argument against privacy, it comes with a lot of false assumptions. For instance, that such information will not spread, that laws won't change in bad ways you can't control, that you can trust law enforcement infinitely and indefinitely, and so on and so forth.

Also, a wise man once said: "In theory, theory and practice are the same. In practice however, ...". What you control is yours, and with proper security measures no power the police or justice system has can break that control. That's as it should be.