This is a good post. As much as it might make sense to not have defined roles, the players aren't necessarily going to be comfortable with things being run that way. The closer spot means a lot to the players, even if it shouldn't. To them, it's a coveted position to be earned. You have to put in your time, prove yourself, and maybe after a few years you'll get a chance. In Cecil's mind (and and likely the rest of the team's), he's earned the spot. He's the longest-tenured member of the pen, he's been dominant for two years, and he was anointed as closer in March. To pull him from the spot after one game, and hand it to a rookie who hasn't pitched in AA, is going to piss him off. And it's going to piss off a lot of vets on the team.
He's managing people here, not numbers. I've always appreciated his pen management, but haven't been on the same page with him at all this season.