Only certain local news affiliates are required to use live captioning services. The rest can use Electronic Newsroom Technique (ENT), which creates captions from a news script computer or teleprompter. As the FCC site points out, "because only material that is scripted can be captioned with ENT, breaking news, sports and weather updates, and live field reports are typically not captioned when ENT is used."
All national news produced by ABC, CBS, Fox, and NBC cannot use ENT. Their local affiliates in the top 25 markets also must use live realtime captioning services. In addition, cable news providers that serve at least 50% of the people in the area who subscribe to cable services cannot use ENT.