It would make more sense for them to do away with conferences and have each team play each other 3 times. That way the standings would be perfectly balanced and you wouldn’t have the “this conference is tougher than the other” argument. Most soccer leagues in the world use a similar format.
The conferences and divisions make it so teams play other teams in their Time Zone more often. And more importantly, early Playoff series will be against an opponent in a Time Zone that is no more than 1hr away*.
This is important because the NBA is played on weeknights. The closer to Prime Time games are played, the more convenient it is for people to watch.