Because e-mail doesn't come with a filter that only brings urgent things to your attention.
But he's still reading e-mail - just not on a monitor. And I'd wager he's still replying to it - though perhaps he has her type it up.
And he's using email to about the same extent that a telegraph is a telephone. (With a telegraph, you speak your message out loud, and then the message is sent via a wire to a recipient, so it is just the same as a telephone, right?)
The tiny minority of new, unfiltered emails that ever actually hit my inbox are usually interesting. And they end up having filters written for them if they're going to reoccur.