HBO go

The COX website brags:

Easy, FREE and Included With Your HBO Subscription!

HBO GO is the new online video service that brings the excitement of HBO to your computer! Watch every episode of every season of your favorite HBO shows right from your computer or laptop. Get unlimited access to over 1400 of your favorite shows, including HBO originals, blockbuster hit movies, sports, specials and more wherever you are now with the HBO GO app for your iPad, iPhone or Android device. Now available  in HD.
It’s easy! To start watching online now, just go to hbogo.com and sign in with your Cox primary account User ID and password.

HBO GO is FREE with your HBO subscription.

I am told I need more than a cable account ($180/month) to access the FREE service included with my HBO subscription,  No where on the COX or HBO websites does it say we need BOTH a cable subscription and a COX Internet package. 

If this is a mobile service to use away from home, why is an in house internet service required?