My circumstances have changed many times and I've often had periods when repaying debt was really difficult, but I didn't try to ignore it and walk away from it, which some on this thread seem to be suggesting is a legitimate course of action.
With regard to the lenders selling on the debt - they wouldn't do it if there hadn't been a breach of the original agreement, so again your argument doesn't stand up (plus it's probably in the Ts&Cs that were originally signed that most people think they don't need to read).
The debt collection agencies are not "preying on people's misfortune", but will be reminding people of their responsibilities. As others have said, if you speak to most companies rather than ignoring the problem, then they will be more than happy to get something rather than nothing and you won't end up with a third party to deal with.
Companies using debt collecting agencies is no different to using a solicitor to deal with a dispute on your behalf. You use people with the right skills for the job. I know there are some that are just nasty to deal with (a bit like the CSA!), but the best idea is to avoid getting them on the case in the first place.
Once again I agree with your sentiments BUT I've seen first hand the underhand tactics DCAs use to try and get money out of people. Agreed those people should have contacted the original lender as soon as they couldn't afford the debt. DCAs are mainly funded by Private Equity companies who are already extremely rich and want to become richer due to peoples misfortunes.
It's time lenders and borrowers took responsibility for debts rather than scum companies looking to make a quick profit on people who have hit hard times. I exclude people who have spent beyond their means on purpose.