I believe that the following is currently true:
Neither DISH nor DirecTV enforces the phone line requirement on multiple receiver accounts at this time. Though no guarantee what they will do in the future. Plus, sometimes you will get different answers from different phone reps.
Yes, impulse PPV purchases do require phone line connection.
DirecTV does require phone line connection for some pro-sports packages (Sunday ticket comes to mind), and for some sports channels
Of course check with them for current info....
Moving forward, there are a few obvious problems with their phone line requirements..... Sometimes there just is not a phone connection near the receiver, and some structures make hard-cabling difficult, expensive, or aestetically problematic - particularly when the customer really does not want it
, yea, wireless phone jacks can sometimes help, at a price.
And... then yes, here in the good ole USA there are many homes without land line service. And there is quite a trend of people moving away from traditional plain ole telephone service in favor of cellular/PCS phones.