Captions are no longer just for the hearing impaired as viewers often turn on captions because of a noisy room, to improve understanding, or when the local language is not their primary language. Public venues like airports and restaurants rarely make the audio available so captions provide understanding and context.
Delivering legally required captions for both live and recorded programming can be quite expensive and often difficult to accurately budget. In the US, captions are provided by highly trained stenographers who spend years developing their skills but the supply of trained professionals is on the decline resulting in a shortage of qualified captioners.
In other countries, broadcasters often hire their own captioners and spend weeks training them to provide live captions using a technique called re-speaking.