Two things come to mind (as a homeowner of a fixer-upper).

First, a lot of home repair (not all, but a lot) is small, simple, and fairly commoditized. I used Homeadvisor last week, for example, to repair a broken window, and I wanted it fixed basically as soon as possible. I really just needed a guy with the tools to come in and do the job fast, and Homeadvisor found me that guy quickly.

Second, it's hard to find a good contractor. I'm on my third or fourth plumbing change right now, and have used different plumbers each time. They were all fine, but I haven't yet found someone who I'd absolutely call first. Homeadvisor gets my business until that person comes along.

Don't they also live off once in a while kind of things? A plumber once through the site is a much larger chunk of $ even if I call the same plumber the next time.

I don’t have a regular “Sheetrock repair guy.”