Well, thank you very much for letting me know that the focus of the ATP is solely on America. Not every country has hundred's of choices at the click of a button and even in those other countries that have pay-tv (as we call it) available ,the number of people opting for the service is far from overwhelming. So there you go, you've got a captive audience already.
As to shorter attention spans, not all of us think it's a good thing and not all of us believe it is an integral part of the television experience. Marius has mentioned golf as a positive example that people will stick with a product and I could just as easily use Cricket. Now, there's a sport that doesn't reach a conclusion (and sometimes the conclusion is that there is no winner) for 5 days but people watch. Travel to the participating countries and you will hear it on television sets from start to close of play. Hardly an indication that sport can't hold an audience over more than 3 sets.
People are turning away from the sport not because there is anything wrong with the actual sport itself but because the game has no sense of continuity. When Agassi is gone the link to the past is Federer and that's it. While the skills may be more polished nothing remains of the game's beauty. Tennis has been allowed to become monotonous because the element of risk has been removed, partly through the slowing down of courts and largely through the inability to regulate equipment. Now, ironically, the only chance to see players fully test themselves is in doubles, the game you'd effectively wipe out.