There are two ways of looking at rankings. Being highly ranked throughout the season is indicative of how well your team has done - throughout the season. And yes, that IS important in the team concept.
However, those rankings don't mean anything when the tourney starts as it's anyone's game at that point. Well, theoretically anyway, LOL. And they really don't mean as much pre-season because any team has the opportunity to rise based on their schedule and record. So in that case, they don't mean that much.