I've recently seen calls for volunteers to provide subtitling and captioning, e.g.,
http://blog.universalsubtitles.org/volunteer/Volunteering is a wonderful thing.
Warning: rant ahead.
Would PBS rely on volunteers to provide audio for their news? Or handling the studio lighting? Perhaps the reporters should work out of the goodness of their hearts?
Subtitling and captioning require skill and time. Why should subtitlers/captioners not be compensated for their work? Why should professional TV production consciously exclude viewers for whom audio isn't the appropriate channel? In addition to people who can't understand audio due to deafness or hearing impairment, there's foreign language learners, people in bars, folks running on their treadmills at the gym, and (perhaps most important in this age) Google and other spiders who index and archive video via the caption info.
While some of the Amara projects are non-profit NGOs, others are HUGE corporations, e.g., Google. Yes Google, which has been displaying mostly inaccurate machine-translated captions (some video has been stripped of the professionally prepared captions).