Because DC Comics doesn’t want the NBA profiting off of their imagery without some form of kickback: “Two days after the 5-7½ Robinson spectacularly won the Slam-Dunk competition during All-Star weekend, the NBA announced plans to release a green Krypto-Nate T-shirt for sale at the NBA Store and One day later, the NBA scrapped its plan because of intellectual property issues with DC Comics, the originator of the Superman comic books. DC Comics’ offices are located on Broadway, near the NBA Store. Robinson’s Krypto-Nate scheme – designed to topple a red-caped Dwight Howard and his Superman shtick – was too close to home for DC Comics. Kryptonite is the green emerald crystal found on the fictional planet Krypton that weakens Superman. The NBA is now looking to involve DC Comics in future Krypto-Nate endeavors, according to a league source.”