But that's not the reason they're doing it. Warrior isn't a separate licensing issue and is part of the game. Jordan and Barkley had agreements that superceded the union rights to use thier likenesses. They weren't even offered in the game from what I remember, either was Barry Bonds for the baseball video games. They weren't available by pre-order either.
The Warrior issue is simply a cheezy attempt by video game manufacturers to try and get everyone to pre-order. And to try and protect themselves if the game is crap with the first day reviews. Give the gamer the choice to pay a little extra immediately after the game comes out. People will still preorder if they want Warrior for free.