When you have interest in a Game, you are promoted to search for the topic. When multiple topics come up in the search, all listed by their start date since you check by title, this is confusing. People post in the wrong topics. That is a problem. Instead of making a whole new topic, we keep as few as possible so people don't go "I wanted to talk about this game, but I couldn't find the main topic." This is the main topic. The only other one is locked. Do you understand now?
And you will say "There's only three topics, so shut up." So it is okay to make a new topic whenever you see fit? Anyone can make a topic, and clutter is easy to accumulate.