Sherlock Holmes is the index case for serial fiction featuring the same characters through a long number of stories. (Though The Odyssey and myths about Hercules and Theseus could be elaborated upon and sliced up to make a TV series and the same is true about some Chinese stories such as https://en.wikipedia.org/wiki/Romance_of_the_Three_Kingdoms and https://en.wikipedia.org/wiki/Journey_to_the_West)

It is great commercially because fans will eat it up but I think many authors aren’t happy with working under the constraints it brings.