WhiteElk: i realize my post above (#18) is off the topic. i'll edit as OP wishes. More to the threads point...
i too ponder trends. Hair and clothing styles, music and story telling, language and art, etc. i've many thoughts on this which will go unsaid here, but far as some of the why of it, i tend to think towards our ego minded species seeking change for the sake of it. Some motivations may include a feeling of elitism, sophistication. That by nature we measure our worth against others. That to feel satisfied with self we seek to judge self as superior to others.
On the micro subcultures level we certainly can see that people of one group will feel superior to others. Be it length of hair, birth place, skin color, sexual identity, religious and ideological associations, etc. All these things people use against others in ways which reek of elitism. Perhaps this works on the macro scale of civilizations as well. That even among our own affinity groupings, we must be different than those who came before.
I don't think that post was irrelevant at all. It illustrates a great point. Even when people and turned and smiled at cameras or horrible graphics displayed a show's title, sometimes we didn't like it even back then. We have a huge ability to forgive things we don't like when we're being entertained.
So, that's my two cents to add: sometimes the things weren't liked, they were just done. Sometimes to identify a genre (like the classic protagonist turning around, facing the camera and smiling), sometimes just to fill space and at other times, just as the OP said, a piece of the evolution of television.
Things started with story-telling, then theater, then movies and then television, and several different sorts of iterations on each. And sometimes we carry the dirt from previous mediums to the new.
What I love about today is the Netflix effect on the television. I really believe that it's the future. You get your entertain when you want it, how you want it. You don't need to suffer through commercials (not great on their own, horrible if you have kids) and it doesn't cost much at all. And now Netflix is making shows that don't fit the standard "Fit everything into 30 minutes -- stretch or shrink, we don't care -- it needs to be 30 minutes!" crap. Yay Netflix!