Not all paths in the NCAA Tournament are equally difficult. The entire structure of the tournament is based on the idea that the better teams (i.e. higher seeds) are given the easiest draw. But sometimes upsets occur and the occasional No. 15 seed wins a game (or three), busts the bracket, and clears the path for a No. 8 seed to survive to the Final weekend. Furthermore, not all No. 1 seeds (or No. 8 seeds or No. 15 seeds) are equally strong.
Source:The Only Colors