Not everyone has access to the latest and greatest. I have no cable (unavailable) or satellite (unreliable in the extreme in our area). There is no connection between my internet and my TV, and the 'net is far too slow to watch streaming video of any kind. I do have a DVD player (and two VCRs). My circumstances are not unique outside of urban/suburban areas.
All of this is to say that the DVD market has not yet dried up. I will--and do!--pay for discs because I can't watch anything any other way.