Why was the Monkees' TV series canceled?

Answer 1

The group had grown tired of the formulaic half-hour sitcom, whose episode plots were basically the same; "Davy fell in love with a girl whose uncle was a crook", as Micky Dolenz later recalled. Even during the second season, they stopped taking filming seriously, and sometimes just "walked through" the scenes.

The Monkees hoped to change to a full-hour variety series, presenting other artists with them as the hosts. NBC and Screen Gems weren't interested, and told them they could do another season as-was, or be cancelled. Davy Jones said later "We decided to forget it."