Dollhouse

Why do intelligent TV shows get cancelled all the time?

When this show moved away from single episode arcs, revolving about the assignments, and turned to handling complex themes like - how does one deal with the ethical questions around this kind of human trafficking (-> self-deception, mostly) - what makes a personality - how does an Active cope when confronted with the fact that apparently s/he gave up his/her personality willingly - what makes one give up his personality and allow oneself to be dealt with like a "thing"

Dollhouse became a truly fascinating show. Yet entertaining, captivating. Which of course led to it being cancelled. Oh, sigh.