Still trying to pump some life into this one.....
I had a big long post, but I broke it down in more simple terms.
In the past people were conditioned to certain expectations in their entertainment through limited access. As the entertainment industry as grown and evolved people have become more conditioned to having an open mind and better understanding of narratives because of increased demand and enormously increased access to different varieties stories. People are conditioned now more than ever in the past, especially the pre-cable television past, to desire a wider variety from their entertainment than just the formulas fed to them by a handful of entertainment corporations. Because people were conditioned by the industry they stigmatized things that didn't fit within the parameters of the formulas they had been conditioned to. People are still conditioned by corporations, but now more than ever people are aware the conditioning is happening.
[I know that isn't short, but you should have seen what I wrote before - a basic history of television and expanding entertainment knowledge.]