The reasoning would be financial: the pair are owed over $12 million combined in the 2013-2014 season, and it doesn't seem worth it. Considering their games were built around explosiveness -- the Matrix was once a quick leaper capable of averaging 20 and 10 and Vince Carter was a high-flying scorer and dunk contest legend -- both have aged rather gracefully, still chipping in double-digit points roughly a decade and a half into their NBA careers. But its a rather steep price tag. The 34-year-old Marion is still useful defensively and was a big part of their 2011 NBA Finals win. He currently leads the team with 8.2 rebounds per game, while the 36-year-old Carter is fourth on the team with 12.7 points per game.
There was talk that Mark Cuban was willing to open "the bank of Cuban" to make a deal to push his team into contention, but that hasn't panned out. That was somewhat dependent on Dirk Nowitzki's return making Dallas somewhat relevant, but instead, they're 7-12 in the 19 games he's played. Now they're 20-28, with over five games to make up just to make the playoffs, with less than half a season remaining. With that in mind, winning now doesn't seem too important for the Mavs, and they might be best suited to get themselves into position to make a play on the free agent market this upcoming offseason -- Al Jefferson is the biggest name available -- or set themselves up to take on a star on the trade market. Either way, it doesn't seem necessary to keep a pair of former All-Stars in the fold if the current season doesn't hold much hope.