Can't view subscribers via Users > All Users

Folks subscribe to our blog via the Blog Subscriptions Jetpack Widget. When they subscribe, we see them listed when we go to Jetpack’s Site > Stats and scroll down to view Subscriptions. But we don’t see them if we select Users > All Users. Why not?

Where this is causing us a problem is with AutoChimp. On installing AutoChimp we find that it does a fine job synching the records found in Users but doesn’t seem to know about the folks who subscribe via the Widget. Can you point us in the right direction? Many thanks! Michael