This completely disregards the number of politicians and newsmakers using Twitter as a platform to share information. The US President has been the first president to announce major policy changes over Twitter without any consultation with his own administration.

News outlets cover Twitter precisely because people are making news on the platform. There is a lot of misinformation out there (especially from the President), and major news outlets make bad calls when running stories (affecting their reputation), but their insistence on using Twitter for news isn't a part of that.