Except that people do not typically do that, and it is reasonable to expect that a filing cabinet will contain only important or current documents. With GMail, you typically see personal messages that date back years, probably long before whatever crime the person is suspected of.

"The problem is the amount of information consolidation modern technology enables and encourages."

I think for once, we might agree. The relevant laws were written with a very different model of communication in mind.

If H&R Block had Whitey Bulger's tax returns, would the warrant be required to describe those documents, or, would all of the small, baggable disk drives at their data center be subject to seizure?