I can certainly see where you're coming from. Seen Matthewmatosis say something similar too- to him a PlayStation is just a thing he needs to buy every gen to play 2/3 specific games like Bloodborne and Persona 5. And then just sit there doing nothing.
Can't say I agree but with Play Anywhere it's worth discussing I think.
The guy bought the hardware because of 2 exclusive games
If that's not a strong enough argument to understand why exclusives exists, I don't know what is
Sony makes machines. And they know that by selling the hardware, even if the customer just want to play one game, they may probably buy something down the line on the PS Store.
It would be much more proffitable than just selling the game on another platform.
I understand that it would be much better to be able to play everything on one platform, just like it would be awesome to watch every movie on Netflix
But that's capitalism for you