Tell me the reason it is necessary for the project to create ANN on bitcointalk.
Although depending on different projects they have their own channels to discuss their issues privately, so I don't think it is an important issue.
indeed, its not necessary for a new project to create an announcements thread in this forum
but its better if a new project have it, because this forum is the right place to give informations about that
Time has changed. Some projects can promote their platform via social media alone and they are happy with it. Though there is advantage if they can post their project here in the forum as it is is the center point of most crypto users. And some of them have already backing, so they think, their own marketing is more than enough to gain potential users.