Comment by bluGill

TV has always been about characters - they couldn't do a plot well because they well knew regular viewers would once in a while not be able to watch an episode and so they can't found on your knowing what happened last time - people would miss. TV needed a way to get people to watch as many shows as possible, and that meant getting you involved in the characters, and write stories that could be watched in any order.

Movies meanwhile had a long time between the next one and so you couldn't get people deeply involved in the characters. However you had enough to pull off a slightly complex plot and so that is what movies did.