Making a stop motion animated film is quite an ordeal. From Rudolph the Red Nosed Reindeer to The Nightmare Before Christmas, these films take an incredibly long time to complete. Animators working on these projects must move character models ever so slightly to get a naturally flowing look. Recently, stop-motion film The Boxtrolls showed viewers via time lapse photography the incredible amount of work that goes into making these films.
I bet you have gained a new understanding of the difficult work it takes to complete a stop motion film. Also, this probably answered your question of, “Why aren’t there more stop motion animation films?”