500 is effectively unlimited compared to the 22 GB that AT&T throttles you at on their native plans.
My Cox internet also had a 500 GB warning.
Plus, Netflix HD streaming is about 3GB per hour. You can stream a two hour movie every night and only use 180 GB per month. I've never gotten to 500 GB, so it's effectively unlimited.
If it's good enough for you, I'm glad. But imagine someone that replaces a TV on in the background with an internet stream. Now 2 hours is 6 or 10. Then multiply that by multiple people in a household.
It doesn't take abusive behavior to hit a limit like that on a home connection. If you took a 2007-era 250GB cap, and kept it price-constant, you'd be looking at something like 20TB caps these days.
My Cox internet also had a 500 GB warning.
Plus, Netflix HD streaming is about 3GB per hour. You can stream a two hour movie every night and only use 180 GB per month. I've never gotten to 500 GB, so it's effectively unlimited.