I've got a dozen emails in my inbox right now from friends, contacts, and organizations like the choir I sing in.
And I think there's a lot of truth to it. I don't quite buy the junk mail argument -- I publicly publish my email address everywhere because junk mail is generally a solved problem -- however I just think there are a lot of other options that have added value or lower friction.
A big personal use of email previously (5+ years ago) was the sending of pictures. You know -- the relative that sends you the 20 5MB pictures. Thankfully that is a thing of the past now, and people either post them on Facebook, Flickr, etc.
How about sharing other types of files? It was a major problem when Outlook started banning a lot of file types because that impeded how a lot of people used email. Now every uses Dropbox and other avenues to distribute files.
Perhaps the reality is just that email was, for a time, used for a lot of things that it wasn't appropriate for, and now it's back to its core value.