I'm not advocating high usage for him, but there's going to be games (in the playoffs) in which LMA and/Kawhi are struggling/facing doubles all game, so we need that additional scorer, preferably a perimeter scorer, who can help relieve that pressure. I'm behind Parker so strongly this season because when he's in form (not necessarily scoring 20, but pressuring the defense with penetration and probing), the Spurs go to another level.
As we know, a huge factor in the 2014 run was Manu's resurgence, but I just can't expect a 38 year old with that kind of play style to even be a consistent double digit scorer in a late round playoff series. Patty can indeed pop off, but he matches up terribly all around with Golden State.