well that may be true in PTV’s era when each scene was recorded after rehearsals and they only recorded few episodes before drama went on air. In today’s times, this may not be true for all projects as most of the production houses sell complete drama to the channel before 1st episode goes on air.
Besides, in old days people used to follow drama more than this as there was only one channel and producers know which show was getting most viewership. Sometimes they even asked about the expected ending from the viewers of a particular drama, but they didn’t base popularity a reason for dragging. Overall today’s dramas lack content and we have a few topics in our dramas with expected story lines.