Cream147 on 03 July 2015
I'm not sure why people were surprised about this, it was pretty obviously going to happen based on the menu layout and in particular the fact that there was a "Rules" tab in the lobby. As others have mentioned, Nintendo probably didn't anticipate there would be enough interest to support more modes.
Edit: But just to be clear - nothing has been taken away from anybody, and it's just a rotation just like the maps. This was also obvious.
