Sitcoms are, by design, all about stasis and repetition. The audience is sold a premise, and then the show has to keep telling stories within that premise until it is either cancelled or comes to an end. Character growth is kept to a minimum, and often resets at the end of each episode. Nobody typically becomes more successful than they already were at the start, and if anybody gets married or has children, it almost always has to be with another central cast member.
This makes it difficult for writers to end a show. If any lengthy arc is essentially against the rules, then how do you cap things off? How do you put a definitive point on something when your goal has been to stretch it out for years on end? In the past, these have not been major considerations; most shows just ran until they were no longer popular, and then were cancelled without an ending. This has changed in recent years and, while I’m sure it terrifies some writers’ rooms, it has been used as an opportunity for others.
