Unless you happen to be some kind of big shot with more money lying around than a ten-year-old Animal Crossing save file, you've probably never realised that the Switch actually has a limit on how many games can be downloaded at the same time.
Apparently, if you try to download more than 64 games at any one time, the Switch will show an error screen and refuse to download more until others have completed. To be more precise, this limit applies to just the downloading of games (as far as we can tell) and doesn't relate to purchases, meaning that it's actually possible to stumble across this fact by redownloading all of your already-purchased games in one go.
In all honesty, we had no idea that this limit was even in place, but Reddit user, u/NMe84, has shared a story demonstrating how the bizarre situation came about.
My SD card was full so I ordered a new one. Sadly I didn't have a card reader lying around to copy my games to the new card so I figured "what the heck, I'll just download my games again." Big mistake, as that meant having to open every individual game and tell it to redownload. The new 8.0 feature wasn't much better, sadly.
Anyway, once I tried to get my 65th game to start downloading I got the error in the screenshot. There is apparently a hard limit of 64 games that you can queue for download at any given time.
According to Nintendo, the majority of error codes beginning with '2137' are related to download issues, but specific details are rarely given for the exact cause. Either way, as u/NMe84 notes in further comments, any Switch owners with large game libraries will probably want to transfer games from one SD card to another with a card reader, rather than trying to redownload everything at once.
So, there you have it. Now you can impress your friends with an incredibly obscure Nintendo Switch fact. Never say we don't do anything for you!