For the same reason why anyone ever sat on the bench behind Tebow, Manziel, RG3, or Krappernick. Desperate franchises get blinded by gimmicks and cling to them well past their sell-by date.
What is "studity"?
The Panthers and NFL were ripped to shreds for not putting him in the concussion protocol after taking several hits to the head against Denver. And he was taken off the field this week to check for a concussion after even more hits to the head. And when he hasn't been busy getting concussed, he's injured his throwing hand and ankle. In previous years, he's played on an ankle injury he first got in college and gotten his ribs fractured by Jamie Collins in the preseason.
The way $cam plays - relying on his athleticism, running around, holding the ball for an eternity - is getting him injured by exposing him to contact that smart quarterbacks know how to avoid. And six years into his career, he's not going to change.