Slampman has it correct. I'll take it a step further... I think it's a scam since they can make substations subscription-only if they see fit. The audio codec isn't supported anywhere hardly except the HDHR app and ChannelsDVR. Video and audio quality in my area is unwatchable and the NBC affiliate in Cincinnati appears like it's running at 15fps.
Is there really a future for linear OTA television in the next 20 years? Why would there be with internet streaming becoming the standard? Back in the day the citizens owned the airwaves so why should your legacy OTA stations bother with the FCC when they can stream and charge people for it. Nothing wrong with pay TV mind you, I'm just sick of greedy corporations and virtually all the media outlets on OTA are gigantic, greedy corporations.
I'd be happiest if they simply kept ATSC 1.0 and forced OTA stations to abide by the laws. No need to make my airwaves another profit avenue for the Hearsts and Sinclairs of the world.