You live in Chicago, which has like 23 channels OTA, (and great programming I might add). That is just NOT the case all over the U.S., and you have to understand that.
I live in a rural Michigan area, almost dead center of Michigan lower penisula. Since tv went digital, I can receive exactly 4 channels OTA. Three of them are ALL the same network, in 3 different directions! If the wind blows a tiny little bit, they digitize in and out, even with 100% signal. It SUCKS!
I have a new larger antenna with an amplifier, at the top of a tower, with a rotor. I used to be able to receive like 14 channels that were very watchable, but that went out the window with the digital transition. Believe me, there are LOTS of people in my boat, all over the U.S.
To install a good OTA antenna system from scratch, with at least a 30-40 foot tower, (too much wind on average around here, a rooftop antenna on a tripod would tear your roof off, and I used to be an Winegard installer and KNOW this) guy wire, rotor, coax wire, antenna, amplifier, you are looking at an outlay of at least $600+ retail IF you do it yourself, and don't get killed doing it. Want to pay somebody to do it? $1,200 minimum on average for our area.
It's a lot cheaper to go cable or satellite, and a lot less hassle.