College football scheduling is strange. Future games are announced to the world a few years in advance, and in the years before a game is (likely) played, the conference landscape has the potential to totally change.
So a headline like "Notre Dame agrees to series with Mark Twain Central in 2023" is neat because wow, the Riverboats have never had a home-and-home this big in their young existence. But it doesn't mean an awful lot until the season in which the game is set to take place. At any given time, due to external factors beyond fans' control, the series could disappear because of the ice caps melting, or college football being played in space, or a conference schedule expanding to nine games per year.
The latter is what seems to be happening with the Michigan State-Alabama series originally set for 2016 and 2017. According to the Detroit Free Press, Alabama canceled the potential matchups, which would have seen Nick Saban come home, so to speak (Saban was the head coach at Michigan State from 1995-99 and coached defensive backs during the Reagan era):
“Alabama requested to cancel the series due to uncertainty with the SEC schedule,” [Michigan State athletic director Mark] Hollis wrote in a text message today. “While disappointed, in the spirit of collegiality, we agreed to the request.”
Everyone is supposed to feign outrage and say things like "BAMA SCARED PAWWWLLL," despite the reason probably being that Alabama wouldn't, in fact, have had room to play the Spartans if the SEC adopts a nine-game league slate. The only issue here is that this would have been a nice nonconference battle, and fans need more of those. Attendance is already down across college football, and part of that stems from teams scheduling opponents such as Savannah State, contests in which the favorite ends up winning by so many points that the fourth quarter gets shortened.