Everything is relative.
Netflix compares poorly to a $200 cable package.
It compares very well to raw broadcast TV or even broadcast TV filtered through a Tivo.
Plus antenna reception is a very tricky thing. It's often far from perfect both in terms of the channels you can get and how well you can get them. It's very much a YMMV proposition and is a very fussy sort of thing. Most people don't want to mess with that crap. That's why they have cable.