So, this has always been the cause of some serious resistance to the idea that came up over the years, but now I really feel some of you are now more open to the idea, realizing what does that really always meant and where it came from.
There was the argument that going third-party would be bad for Sony, because they do have no good games. But with the release of Horizon: Zero Dawn and previous great games like Uncharted and The Last of Us nobody can take that position in seriousness anymore. So selling these games to the expanded audience of PC-gamers should really increase the sales numbers and could make Sony some serious buck.
These games were also always held back from the console-hardware. On PC they could really shine technologically.Think what would be possible on PC, if it isn't held back by years old console-hardware!
Also PC aren't anymore complicated. Steam is easy to use and PC in general are way more easy to use. So a usual counter-point to PC is also not true anymore in this age and time.
If Sony gave up producing own console-hardware, they wouldn't need any longer to throw any manpower to tasks on the OS, on browser, streaming-apps or other stuff that has to be provided to give a full console-experience. This manpower could instead go to producing games too.
And Sony's games would easily fit on PC. They do not use normally special input options like motion control or NFC which would not be readily available on every PC, but standard-controllers which every gamer owns. So the games could be easily produced for PCs.
That would be a win-win-situation. Gamers could profite from more advanced games not held back back hardware multiple years old and Sony could really increase sales on it's games and could a buttload of money, which they could invest in even greater gaming experiences.
And if you think: nah, Sony never should go 3rd-party, just imagine Horizon, Uncharted, TLOU, The Last guardian, God of War, ... in 4K and 120 fps. With much more details and effects they do have now. Just imagine.
EDIT1: Many of these arguments certainly apply to Nintendo and Microsoft too, so the same could be said about them. I made it for Sony, because Horizon recently made me longing for a PC-release of the game.
EDIT2: As malistix1985 points out, we could get rid of paid online with this. Thinking about it, PC-releases also usually make modding and user-created online-server easier to achieve. Only wins surrounding this idea.