Because this whole kerfluffle is about the fact that by granting Google the ability to spam-filter and process your email, you are giving up your legal expectat

Because this whole kerfluffle is about the fact that by granting Google the ability to spam-filter and process your email, you are giving up your legal expectation of privacy by placing your data into the hands of a third party. It's the lowest common denominator. Sure, they may be doing other stuff, but we know for a fact that they process your email in ways X, Y, and Z, which are what the legal theories are based upon.