Stern happened. Ever since he has been the leagues commissioner he has done everything in his powers
to snuff out 3 great things that were once the heart and soul of the NBA;
*The natural aggression and contact that (should) come with any physical and highly competitive sport
*Man to man physical defense
*The center position
If you watch 60's documentaries about the NBA when it was still trying to be promoted (before it was big-time like today) one of the selling points the narrators of NBA films ALWAYS point out in every old film reel was "And don't let anyone tell you there is no contact in NBA basketball!"
(then they proceed to show fighting/shoving/elbowing/falling/tackling/dirty plays etc).... I mean, they were once using the NBA's most physical or violent moments as a means to SELL TICKETS back then. Eventually they succeeded and the NBA became bigtime by the early 1980's and Bird and Magic's era is the most well-documented version of pre-sternball. And surprise surprise, most people LOVE watching those highlights from back then - there is so much more tenacity and natural physical play happening back then.
All his rules he has ever made since climbing the ladder was for his agenda to eliminate those three things and turn the NBA into a more PC mass-marketable ("safe for everyone") PG-rated soft sport - so that he can accumulate more advertisement revenue. No hand checking, no glaring, no bad mouthing... nothing. You might as well broadcast modern NBA basketball on the freaking Disney channel with what he has done to it.