That's if you want it enabled, no? I know that not all apps running on a PC will show up in your Discord status unless said app is compatible with such feature. For example, not all emulators would show up if I had one running, the devs have to integrate that.Showing what application you are currently running is a Discord setting. It is not integrated by the game dev.
Alternatively, Discord has had some deals with other companies to make it easier for recognition and implementation of those apps, like Spotify. Those are bigger names though, the more mainstream stuff.