Because Star Trek isn't just some show. It's a broad vision of the future. A very hopeful and desireable future of how humanity could grow up and join the cosmos. When you listen to someone postulate about the future and you hear ideas that you can agree with, then that spawns more conversation and theory. It basically compounds on itself. Of course a lot of star trek isn't really anything but a story. But it's the few elements that are very technical and whatnot that really set the scene.
It does. But there is also a splinter faction of Trekkists who celebrate a triduum of phasers, photon torpedoes and shields; the murderous nature of Klingon society; and, the evil of the Mirror Universe. They're obsessed with it, and, to them, no true Trek lies beyond this.
It's kind of like "Industrial Light and Magic versus Industrial Fire and Brimstone".