I don't think you can separate the decision to sit him behind those guys from his slate though.
The other thing is that it's not just his legal problems which are actually relatively minor, but it was also his attitude. From what I read he always seemed to think he was the greatest thing ever even when sitting on the bench in the NFL.
Starting him could cause locker room problems (giving him a higher profile) and furthermore could make it more difficult to humble him in the future.
Not saying he's the answer, in fact I think we should just assume he isn't. But I don't think you can entirely separate the personal/maturity issues from the decision to not start him.
I wonder if they will have him competing against JB this season? Ballard said he will not commit to JB starting next season. That could obviously mean he's looking for a QB in the draft and/or free agency. Could also mean that Kelly gets to compete.
It is strange that they kept him on the roster. At the same time it makes you wonder though why they didn't give Kelly a chance when we where out of the playoffs to see what we had?
My only thought on that would be pulling JB in the middle of the season even when we don't have a shot at the playoffs sends a message that undermines JB to both the team and the fan base. Sort of a situation where if you are going to make a QB switch you better be sure because switching back is hard to do once that move has been made.