I personally think it's a negative feedback loop: The media caters to the visceral lowest common denominator because that's the broadest most reliable audience, promoting our guilty pleasures till they become merely pleasure. Along the way, deeper/decent fare's marginalized until so unfamiliar to the general public that it's irrelevant or even incomprehensible. Then networks check the results and see that everything critics find most tastless audiences find most interesting (and vice versa) so the whole cycle begins again, producing an endless race to a constantly falling cultural bottom.
The thing is, media's not an essential need like food, shelter and medical care: It's not only easy for us to "vote with our eyes," but that's the ONLY thing that can ever truly change programming content. Networks will always blindly broadcast whatever their research says is most popular; if CSPAN suddenly started leading all the ratings list, every channel in America would instantly switch to round the clock public affairs programming (instead of sticking it on in the early Sunday deadzone when everyone's asleep or in church, and only airing it THEN because their FCC licenses operaton "in the public interest.")
Ultimately, maybe it's just evolution: Animals are conditioned to focus on threat avoidance, because missing something really good's innocuous, but a split seconds inattention to anything really bad can be immediately lethal. So we relate to and easily fixate on conflict and horror, because they innately, instinctively, engage us. We're rational enough to want the experience vicariously; actually BEING shot is far less titillating than seeing it happen to SOMEONE ELSE. But we're primed to react to it in a way impossible for academic discussions of influences in 15th century painting. "Who cares?" is a very real question.
So we're having this discussion on a website devoted to one of the teams in our modern gladiatorial arena, as its administrators struggle to find ways to provide the violent brutality that rakes in billions in annual profits, without losing the audience increasingly aware of and so finally uncomfortable with the real and serious consequences to those involved and those around them. Not sure what the solution is on that score, except perhaps "controlled" violence (bearing in mind, as always, that "control"=/="abolition;" parents should control their children, but not destroy them.)
Rambling more than usual here; probably time for bed....