Unlike other channels, shopping channels pay Comcast to be carried on their systems. Evine has to pay for the HD feeds to be featured. In the last year or so, they paid for their SD feed to be included in many areas in the HD channel areas. In Central PA, Evine put themselves on channel 834, for example.
Evine likely will need to pay more money for the bandwidth on Comcast's system to be carried in HD in the future.