This may surprise you, but many people have high limit credit cards with APRs well below 20%, some even well below 10%. If you have great credit then you can get loans and credit pretty cheap.
If you're in a position to secure one of those pleasant credit cards is it likely you'd be one of the people relying on a credit card as a sole means to survive a sudden layoff? I think you're assuming that because it's easy for people when they're doing well it must always be easy.
There are plenty of people with a good income and reasonable housing costs, and from memory that's about all that's asked for on a credit application. But they spend everything else on vacations and private schools and whatever, so they'd go down fast if their income stopped.
