It depends which family we're talking about these days, I never heard of made guys from the Genovese family for instance, being used as muscle to collect debts, they have associates for that..

But Vince Filipelli, made man in the Philly mob, was twice convicted for violently collecting debts. That can either mean they don't have enough associates or that he likes to intimidate people and use violence. Being that he was a 260 pound Gorilla juice head at the time, that is also very plausible..