I know when I signed up with Dish. I was supposed to get the SD DVR, but they brought me a VIP 722. For nearly two years I only got the "Test" channel in HD, which was HD Theater just labeled test. I refused to pay for an HD upgrade until I was offered HD free for life, if I paid the $10 for the old HD Platinum. I dropped Multi-Sports and went with HD. Funny thing was that I actually had HD on Comcast before I bought my current home and switched to Dish.
The moral is, I'm just one person. I bet there are plenty like me who might be equipped for HD, but just don't subscribe.
Also, I wish I still had the channel lineup card from 2008. Because, I specifically remember the VOOM channels being in either the highest HD package or second highest. Meaning that not all HD subs today would have subscribed to VOOM. So that percentage really should have an asterisk next to it.
My parents are in a similar situation. The switched to EA due to LOS, and thus now have a 722. They get HD as that is the only version of many channels on EA, but only have SD TVs and don't sub to HD.
The 2008 card with Voom on a separate tier was from when Dish was initially citing a breach. THe affiliation agreement required Voom for a certain (and if memory serves, high) percentage of subs. Befor 2008, all HD subs had to get a $20 HD add on pack that included Voom and many of the current Platinum channels.