Because people want reboots:
This concurrent thread is at 91 posts as I write this.
If no one watched reboots, Hollywood would stop making them. But not only is there a passive audience acceptance of them, there’s a positive demand.
There’s also the “elevator pitch” idea. There’s a longstanding belief in Hollywood that you need to be able to pitch your idea in the time it takes to ride an elevator a few floors. That’s gone from a bit of wisdom about studio execs’ short attention spans to a bit of a self-fulfilling truism. A lot of execs seem to honestly believe if you don’t make an “elevator pitch” for your concept, it’s not worth pursuing. And “Reboot X!” is a pretty succinct pitch. Once you get your foot in the door with the elevator pitch, you can explain how your version will be different and improve on the old version. Or not.