Starting on June 27th, 2015, SMS notifications from Google Calendar will no longer be sent. SMS notifications launched before smartphones were available. Now, in a world with smartphones and notifications, you can get richer, more reliable experience on your mobile device, even offline.
The real question is why this isn't a win-win for their customers anyway?
It's not a win-win for customers unless the price goes down. It may be just a win if there's a reduced likelihood of NSA surveillance, but there's no guarantee of that.