Now consider what is at stake in the Eastern Conference. The team that finishes the season first overall will only have to play one of the other two contenders, and it will have the home-court advantage. Everything else being equal, that is a very desirable place to be.
The teams that finish second and third will have a war with each other, and then the winner of that series gets to play the (probably well-rested) number one seed. The third place team, in particular, will have a much greater degree of difficulty. To get to the finals, it will have to defeat the other two contenders, and not have the home-court advantage in either series. Moreover, its first-round game against the sixth seed will likely be against a superior team to what the other two contenders face in their first round match up. So a matter of finishing ahead or behind in the East by simply one or two games can dramatically alter the odds of a team getting to the Finals.