Sony has announced that it's walking back the mandatory PSN requirement for certain PlayStation games on PC, and what's more, you'll get in-game incentives for those titles if you do decide to link a PlayStation account.
In a PlayStation Blog post, Sony says that beginning with the PC release of Marvel's Spider-Man 2 - which is due to launch tomorrow - you'll get "more benefits to playing with an account for PlayStation Network" on PC.
Spider-Man 2, as well as God of War Ragnarok, The Last of Us Part 2 Remastered, and Horizon Zero Dawn Remastered, will all be getting "in-game content unlocks" for PSN account users, and you won't be required to sign up for a PlayStation account to play them on PC.

If you do sign in with a PSN account, you'll gain early access to the Spider-Man 2099 Black Suit and Miles' 2099 suit in Spider-Man 2, and you'll get the Armor of the Black Bear set in God of War Ragnarok, which was previously only available in New Game Plus.
You'll also get extra points "to activate bonus features and unlock extras" in The Last of Us Part 2 Remastered, as well as a jacket for Ellie themed around Naughty Dog's upcoming Intergalactic: The Heretic Prophet.
Finally, in Horizon Zero Dawn Remastered, you'll get access to the Nora Valiant outfit. Of course, you will need to own all of these games on PC if you want these rewards; they're not forthcoming on PlayStation 5, since you need a PSN account to play on that console anyway.

There is, of course, no mention of any multiplayer games losing their PSN account requirement; games like Lego Horizon Adventures and Ghost of Tsushima will still require a PSN account for their multiplayer components.
Curiously, it's also worth noting that a couple of single-player Sony PC releases, like Horizon Forbidden West and Until Dawn, won't offer any goodies for signing up to a PSN account.
This will, however, likely set a precedent whereby single-player PlayStation games will no longer require PSN accounts to use on PC. We'll have to wait and see whether that's the case for future PC releases. Stay tuned for more.