it doesnt seem like a terribly hard thing to implement.
It does, though, because this isn't Nintendo's side that's implementing it.
The are two ways you can pull this off. You can either do a full push of your RAM to non-volatile storage (the Switch side), which would take too long and take up however much RAM is being used, or you have to force developers (as part of the TRCs/TCRs/Lot Checks) to support this feature and that's very hard (the game's side).
Save systems in games are NOT at all consistent. There's a million ways to write data to the disc, and there's never any consistent rules or logic about it. I'm not saying it's bad, but it does mean extra work for developers and it could mean buggy behaviour if the save code isn't tested properly.
