Maybe thats the case for YOU, but for a lot of people thats not the case.
Why do like most multiplatform games sell a lot better on PS4/Xbox One than PC, when the PC Versions are FAR superior, cheaper, free online, "Shooting with Controller sucks, Mouse/Keyboard are waaay better!" right!?
Oh another example, why is the Xbox One still selling, the same or even higher now than before Xbox Games were still only on Xbox One !
Oh short awnser, a LOT to be exact like 85 Million People and way more to come like to play on Consoles. Maybe YOU see it as a waste and oh god "Why do people buy and play on such cheap inferior devices!?"
Same with PSNow, i mean what you wanted to say is "Why do consoles still exist, its useless now, everything can be played on PC!?"
Well thats what your statement sounds for me and is PSNow better than actually playing Games on PS4, when PSNow is a Streamingservice, you dont own the games, can you even play online (i dont know), can you add friends, send messages, partychat etc. ! Oh and PSNow is btw only available in the UK, Belgium, Netherlands, USA as of right now, so i cant even get it if i wanetd and even if its available everywhere, then no i still wont use it.
At the end of the day, its cool for YOU and other People that you can play Every Xbox/PS game on PC in a way now (or years later), but a lot of people as i said see it different. And also as of now you cant play PS4 Games on PSNow, also Sony never said what Games will come to PSNow, 3rd Party, Exclusives, what Exclusives like Killzone Shadow Fall, Knack and Games like UC4, Horizon, Bloodborne will be added years later so you have to wait a long time to play them!?