Tim, Tony, and Manu are all leaders by example, but none are very vocal about taking the reigns of the team. Only in recent years have you even seen Tim pull the team together or be the guy talking in the huddle. For whatever reason, it's a role that none of them really seems to wants to accept, and that's when they defer to Pop.
Horry is one of the few players who is willing to call someone out, who is willing to hold people accountable, and who is willing to put his experience to work. The only other person who comes close is Brent Barry, but you can't compare Barry's experience to Horry's. And Finley was always too busy trying to straighten out his own head to help out anybody else.
For a team that lacks a serious vocal presence and is bringing in a mix of young or new players, it seems foolish to send away one of your best locker room leaders if he's willing to come back for the minimum. Especially if that guy is one of the most decorated players to have ever been in the league.
Rob's not even playing hardball about it. He's pretty much said he wants to come back here, and it sounds like the ball is in the Spurs' court.