Why Each Team Does This:

Brooklyn Nets: This trade frees up a ton of cap space now and in the future which is needed since Cam Johnson is a free agent and needs to be signed to an extension. This also frees up cap space for the offseason Claxton becomes a free agent.

San Antonio Spurs: They take a chance on a player who was an all-defensive player a couple of years ago. I believe this is the perfect place for Simmons to go because there won't be high expectations since the Spurs are rebuilding, he would learn a lot from an experienced and smart coach in Popovich, and if he really wants to work on his offensive game the spurs have one of the best shooting coaches in the league.