My guess is that it's because SmartTiles isn't secure. It's a strength from ease-of-use, but a weakness from a liability/security perspective. I thought about using it at my house, but then decided against because of its security weaknesses. If anyone gets the url, they are in. Period.
Don't get me wrong - I think the app is AMAZING!!! It's incredible. Again, period. It just depends on your needs.
But I wouldn't thnk ST could put their official blessing on it with the security as it is.