A lot of youtubers and such only make announcements for content and streams via twitter, or their own services that kind of suck worse in terms of access. In order to stay on top of some limited access content, twitter is still "useful" in that regard.
Personally, I've never used it for that, I mostly ever checked twitter when a site I visit or game I play is down and they don't have a good way of conveying details otherwise. But I know of content creators that use it for that, so I'd understand people using it to stay abreast of content that way.