It's unclear why Nintendo quietly added this compatibility, but it does suggest they may have plans to port over Super Smash Bros.to Switch and want to retain compatibility with the GameCube adapter and pad play option.
In order to use the controllers, you will need the special adapter that was released for the Wii U. But the fact that GameCube controllers work at all is going to be very exciting for Nintendo fans who believe it's the best controller the company ever made.
I don't know about the rest of you out there, but when we got our first official look at the Nintendo Switch previous year, my biggest question was how will I play my beloved Super Smash Bros. series? Obviously. They don't have a way of interfacing directly with Nintendo's latest hardware, but the Switch does have USB support. You can find this feature in System Settings - Users - Transfer Your User and Save Data.
Once again, before you get excited, it appears the ZL and the Home button on the GameCube controllers don't work on the Switch.
Almost every Nintendo Switch owner I've spoken to has professed their love for the portable console. However, controls at that time were very much limited, making the controller nearly unusable with most Switch games, notes TechRadar.
We have good news for anyone with old Game Cube controllers lying about. Unfortunately, the Switch has been severely lacking the usual Nintendo functionality during its 7-month life, which is surprisingly longer than it took to bring the feature to the now-defunct Wii U.