That's just the NBA. It's about protecting its stars.
The NBA, moreso than any other professional league, sells its stars. It's good for the league when Kobe and Lebron put up big numbers, so they get calls.
And it goes further than that, just being a decent player and a veteran gets you calls against rookies and 2nd or 3rd year guys. Rudy, OJ, and Marc will get those calls in the future, but they won't right now. That's just the NBA, which makes it all the more impressive when a team like the Grizzlies can compete against the current superstars.