[...]hearing aids are Class I regulated medical devices... I can only imagine the amount of bureaucracy that must be involved to obtaining that classification.
Examples of Class I devices include elastic bandages, examination gloves, and hand-held surgical instruments.
(2) Video programming distributor. Any television broadcast station licensed by the Commission and any multichannel video programming distributor as defined in Â 76.1000(e) of this chapter, and any other distributor of video programming for residential reception that delivers such programming directly to the home and is subject to the jurisdiction of the Commission.
and "any other distributor of video programming for residential reception that delivers such programming directly to the home" sounds like it fits.
The FCC was established by the Communications Act of 1934 and is charged with regulating interstate and international communications by radio, television, wire, satellite and cable.
There are also technical issues; HDMI doesn't have a CC stream so the merge of CC or subtitle and video have to happen in the Roku box or upstream.