What SJ is saying is that every other prep, college or professional sports league, beginning at the start of the regular season, holds essentially a long round-robin plus elimination bracket "tournament" for their championship. For instance the NFL playoffs are really the 32 team "qualifying round" narrowed into 12 teams for the elimination games.
Except of course the FBS (until 2014). Until there was an official playoff for the D1 Championship you couldn't truthfully say the regular season was a playoff, but now you can, because it's basically a 120 team scramble trying to get into the 4 slots based on your "Q round" (first 12 games) results.