regardless of what was happening offscreen between ford and nancy barrett the writers might have just felt the character had run it's course...
by this point "ordinary" male characters like sam, joe haskell and burke devlin were fast becoming a thing of the past. from 1968 on nearly all of the male characters were some sort of supernatural creature either by design(adam, nicholas blair) or by influence (quentin, tom/chris jennings). run-of-the-mill artists and fisherman were passé. as a key member of the Collins family only roger really enjoyed any job security.
imperious matriarchs, lovelorn lady doctors and vacuous ingénues were in it for the long haul but for the guys it was pretty much monsters or nothing from this point on.
