Ask HN: How does turning off my ad blocker help?

Websites often say things to the effect of “our site looks better with ads, turn your blocker off, you monster” and “please help feed our starving families by not blocking our ads.”

To me, this sounds as if a TV show or station would be asking people not to mute the commercials.

How does me not blocking ads help the “good guy?” Is it just the fact that I could click on an ad, even though I don’t intend to?