Making small payments on a personal debt can buy you time.  It prevents people from getting very mad and trying to take you to court, get more info about you, and spread the word of what you did to the general public.  Over time, people also get weary and are liable to forget/forgive debts.  Just look in this thread how many people were owed one amount and settled for 1/2-1/3rd that amount.  That's pure profit for Bit365.  Also after a long period of time people think "well it's been so long, there's nothing I can do now".  It's pretty common for people to be strung along with small payments.

The problem is, it also looks the same as if someone was getting periodic payments (paycheck, ad revenue, ect) and was legit trying to make good on the debt.