Well, you can't do it if you're not always home...and lots of people have reasons to be away.
I'm confused as to why you say killing the rats isn't working. They used to have multiple rats, and now they're down to one, maybe two, at a time. In any case, I never said it was impossible. I said I'd be interested in what the other methods are. I don't actually know everything they've tried, so I thought I'd pass the ideas on. You seem to think that I have some sort of vested interest in killing the rats, simply because I don't think it's a big deal. I don't. I'm not sure what I'd do in their situation, because having to actually dispose of a dead animal makes me sick. (This applies when I've lost pets, too.) These particular people tried a few things - I don't know what all of them were - and then went to "traps" that kill. That worked. That doesn't mean there wasn't something else that might have worked, too...it just means they didn't find something.
To be honest, most people I've known who have tried non-fatal methods of dealing with pests have had very, very limited luck. That doesn't mean I don't think it can work, though.
The problem really with using only fatal methods, or even methods that try to repel, is that it doesn't address why they are there. If you figure that out then you can keep them from coming back. Hopefully.