Because Jeff is funny.
"Maybe women are completely different when we’re not with them. Maybe they’re not cross all the time."
"I need breasts with brains. I don’t mean individual brains, obviously... I mean, not a brain each. You know, I like intelligent women, but you’ve got to draw the line somewhere... I think breast brains would be over-egging the woman pudding."
This is why there are two points of sadness in my life. 1) Jeff was not in the 4th season of Coupling. 2) Coupling appears to have departed to the great TV Tome in the sky.