Why are there so few episodes for a show that ran for nearly a decade?

Here is the definitive breakdown of the Sherlock episode count.

1 episode ("The Abominable Bride") — a Victorian-era special that bridges the gap between series 3 and 4.

3 episodes ("The Six Thatchers," "The Lying Detective," "The Final Problem") The "Hidden" and Bonus Episodes

However, as of 2024, there are no plans for new episodes. The creators have stated that the schedules of Cumberbatch and Freeman (both now major Hollywood stars and Marvel alumni) make a reunion difficult, though not impossible.