Or because consoles like the Xbox360 had a control pad.... only.
Consoles for ten years set the bar and a mindset was formed in part by hardware limitations, input limitations, Licencing limitations and greed. The largest market for any developer to make a game and profit from was the console market which was a limited and walled garden for ten years. PC gamers got the table scraps.
Steam (for example) helped provide a platform for the indi developers and crowd funded titles in an open PC market place and managed to keep alive and resurrect alot of these game types. Now we see Indi games appearing on consoles as they play catch up, but still limited by the above mentioned ingrained limitations of the console cosm.
Consoles are cheap, they are easy and they are popular. There limitations shaped the gaming marketplace for ten years. The Xbox 360 generation is a good example of how a gaming platform can hold back the progress of gaming technology.
Which Scorpio and Windows 10 is now helping to remedy... but they did create the problem initially. That said, Scorpio is nothing but a "mini-PC" to begin with- albeit with a proprietary ROM hardware interface to prevent people from flashing them and using for whatever they want to. The more consoles "upgrade" themselves, they're just eventually moving closer to what PC's are already capable of.