In the past few years I have noticed that some TV series are not being sold on DVD. Some series have the first and second season sold, but not others. Some other shows are not sold at all. What is the reason for this?

With a few exceptions, sales of TV shows and movies on DVD and Blu-ray have been declining for years as consumers embraced digital downloads and streaming services. That diminished interest has prompted retailers such as Best Buy to stop stocking discs, so there is less reason for distributors to make shows available in those forms — especially when a digital or streaming version is far more profitable.