undoubtedly no you don't need to buy a PS4,
you can easily sign up for Playstation Now $100/year had have access to ~400 PS titles on your PC.
https://www.cnet.com/news/playstation-games-are-coming-to-windows-pc/
Alternatively you can still buy that PS4 and still stream and play on your PC with a Remote Play app that you can get.
http://www.pcadvisor.co.uk/how-to/game/how-play-ps4-on-pc-using-pc-remote-play-playstation-now-streaming-2016-3630864/
Even more, is that Steam Beta can allow you to use the DS4 controller for the PS4 in order to play PC games with a console controller that isn't Xbox, or Steam Controller.