> since I get my TV over the air, I can't fathom for a second why anyone pays for TV.
Here are some reasons people might buy cable:
1. Cable has many more channels, many of which don't exist on over-the-air TV.
2. If you grew up in a cabled household, you may think of it as a "standard" utility and buy it without thinking about whether you really need it.
3. Depending on where you live, the over-the-air channels you receive may be limited. I've discussed this problem before on HN [1].
4. Many homes and buildings no longer have antennas for receiving over-the-air signals. Many new TV's have no or poor built-in antennas. So you may have to buy a bulky antenna with no idea how well it will work.
5. If your TV is more than five years old, you may have to get a converter box to receive TV over the air, since TV transmissions changed format in 2009 [1]. New TV's have hardware to read the new digital TV signals, but old TV's don't.
Here are some reasons people might decide against getting, or discontinue a cable subscription:
1. You can save a substantial amount of money.
2. You may spend less time watching TV if you have less content available (whether this is good or bad is subjective, but for many people, reducing TV time is a plus).
3. Losing access to cable-TV content is less painful if you have a broadband connection, because much content is available freely and legally online -- Youtube, Hulu, Crunchyroll, etc. You can usually* send your computer's video output to your TV.
I'm writing from a USA point of view; if you're in another country, your mileage may vary.
*You need the computer and TV to have the same port, and the proper cable. An astonishing number of video ports have come into existence, many in the last 10-15 years, including traditional antenna, component, composite, VGA, S-Video, DVI, HDMI, and DisplayPort. A computer and TV built around the same time are likelier to have the same port, but your best bet is to check the specs before you buy.
[1] http://news.ycombinator.com/item?id=4307147