They aren't employed by the NBA because they scored well on the SATs or anything like that. They are employed to play basketball and that is what they do. As long as they continue to play at a high level, there will be a place for them in the NBA, despite what you or other people may think. Same goes for any other professional sport.
But they are also employed to represent the sport at all times. For example in "soccer" if a player does something off the pitch that shames the name of football, they are commonly banned for "bringing the game into disripute". Being a professional sports star brings the added pressure of living your life as a role model should. It comes with the territory.