In today's NBA, maintaining the same core group of players for a number of years is an arduous task. Free agency plays a huge role, obviously, but as we've seen in the past few years (Dwight Howard, Carmelo Anthony), there are cases where a player simply requests that he be dealt, bucking the natural flow of player movement throughout the NBA.
Money and playing time are usually the biggest factors whenever someone asks to be moved, but sometimes there are certain instances when a player just wants to get out of what he perceives to be a bad situation.
Every man on an NBA roster wants to excel, and those who don't see a clear path to stardom with their current team have a tough decision to make. Recently, a number of them have taken their concerns directly to the front office and demanded a trade, and the same figures to happen this season as well.