I was in 3rd party collections for a couple years, then worked 6 years in a recoveries unit at a bank in the dealer/auto group. I'd say only around 30% of the debtors who make it to 3rd party collections are responsible and decent people who have run into bad times and genuinely want to, but can't pay their bills. Maybe even only 20%. And most bill collectors recognize them and leave them alone.
The rest are deadbeats, self-important "high flyers" or credit criminals.
If someone offers to make a reasonable payment plan, 9/10 times I and the creditor will agree to it because the debtor shows that he/she is acting in good faith.