I can also just wait out the debt period, until it passes the statute of limitations, and not pay anything at all - but I don't, because I prefer having a decent credit score and businesses who will do business with me.
I would suspect most of the people who are defaulting on debts don't have significant assets or income to make it easy to recover debts, even with a court order.
The option to sue is reasonable because otherwise people who are too rich to need credit would often find themselves in positions where there's little-to-no incentive to pay back. But these aren't the bulk of debts that these agencies are working with - the bulk of people who are defaulting on loans aren't people with money, they're people without money.
Frankly the harassment techniques that a lot of debt collectors use are disgusting and they prey on those who already are suffering. The FDCPA makes a lot of these techniques illegal, but the protections the law provides aren't widely known.
