The truth is that the amount of work and dedication that goes into a great emulator, with all the quirks and ad hoc settings for the whole library... no corporation on Earth can get that within months, it's actually a textbook example of the Mythical Man-Month (you need a few "hotshots" that will give their life for years to reach that level of refinement, you just can't hack it with a team of 10x averages without the heart that goes into it).
And even if you could, it's ridiculous cost versus 'free'.
Sony did the right thing by crediting them explicitely in-GUI. It's a classy move. There's a certain school within Sony that's extremely friendly to open-source, I surmise it's the historical engineering ethos of that company that hasn't entirely left their premises— in some buildings, some labs, the Sony-spirit of old is alive and kicking, e.g. their Sailfish-OS friendly phones (i.e. open-sourced drivers for these models, fully rootable etc).
It can and has been done. Have a look at "Connectix Virtual Game Station"[1]. It's a commercial prodcut that played virtually every PS1 game flawlessly on a 233MHx iMac. I spent thousands of hours playing games on that thing, and glitches were very rare in a huge range of games, even the most demanding like Metal Gear Solid.
Jobs even demoed it on stage.
[1] https://en.wikipedia.org/wiki/Connectix_Virtual_Game_Station
I think it's not that easy. Not that corporations like Sony are necessarily lacking, but the greatest emulators are works of art, some masterpieces of reverse-engineering.
Which is essentially the point of re-releasing that, or selling old Nintendo games on the Wii/Switch market -- easy cash grabs with little overhead effort.
