It’s a separate app, not a separate paid app. They didn’t do this for money or any conspirical reason. They most likely did this to streamline the second screen feature into its own thing instead of having to open the “3 in 1” app. I, for one, would rather have this separate so I don’t have to wait for the main app to load. This goes for the Messages app as well: I hated having to wait to navigate the menu just to get to messages, messages should be its own thing. The bottom line is that this does what the main app used to, but without the menu navigation. If you don’t like it don’t download it, it’s not a big enough feature to care about this much.
Although the complaints about it being slow or not conmecting should be looked into. Since they have gone and made into its own thing it should be working perfectly or at the least as well as it would on the main app.