If you are a national sports talk radio host and you are filling a segment - or multiple segments - with an extended kvetch over how the "celebrities" at the NBA All Star Weekend Celebrity Basketball Game aren't big enough celebrities for you to truly appreciate the event, your employers (who are in the entertainment business and thus presumably know something about how this whole celebrity thing works) may want to take a second look at your qualifications.
Point One: It Is Not A Big Deal. You're talking a sideshow to a sideshow to an exhibition here. The potential exposure benefit from playing is minimal.
Point Two: Nobody wants to look bad. Tom Cruise looks great in an action movie. Put him on the court and he's suddenly Muggsy Bogues' body with Chuck Nevitt's game. Celebrity is an aspirational business; look bad in public and you're suddenly a lot less attractive as an object of adoration. So no agent in their right mind is going to let their valuable asset out there if there's the slightest chance he's going to look like he'd lose a game of HORSE to Air Bud.
Point Three: There is no point three. I feel dirty for having written this much on the topic already. It was an exhibition game with a couple of minor celebrities, a couple of celebrities whose brand wouldn't be impacted no matter what they did on the court, and a couple of WNBA players the league was half-heartedly trying to get some exposure for. Kudos to the Secretary of Education for getting a double-double, but really, even if you're desperately trying to get away from Miami Dolphins/Darren Sharper coverage, there's got to be something better to get upset about.