You implied that they supported keyboards and mice natively.
Quite a few games do, as support is dependent on the developer, not the console. A quite few of our games, like FFXIV, have native support for keyboard+mouse. I think War Thunder also has native support for mouse+keyboards. For those games that don't, again, it's a simple solution by getting an adapter that adds support keyboard+mouse support to any PS4 game.
What I am saying is that it's no major feet or big deal for someone to get a keyboard+mouse to work in any PS4 game.