I think it has a lot to do with most of those old shows not having an arc. As much as I love serialized TV it doesn’t lend itself to casual viewing. Episodic TV you can watch any episode any time, you don’t have to know anything that happened before. The rise of serialization has opened many wonderful doors for story telling. But there’s still a lot of audience for 1 episode stories with nothing to keep track of.
-PJ
Serialized brit TV is the best. They do a book until it is over. Not dragged on.