How do debt settlement programs work?

how do debt settler people make peoples debts go away? who pays the money? is it fair that if someone is in debt because they made poor choices that they can get out of paying some of the money? i know not all people go into debt for that reason but a lot do...and why is it fair for the people who work hard to make all of their money and pay everything on their own? again thats not always the case... so where does the money come from for paying all that debt?