Actually, morality and debt do not intersect at all.
Graeber covers this very point in his book "Debt". It's fascinating.
We all have moral obligations to the people around us: to our families, our friends, our neighbors, the people in our lives. We are generous to our friends, and moral obligations will make them return our generosity.
However, when you borrow money, you are making a gamble. If you manage to repay the loan, you will be allowed to borrow again. If you fail to repay, you will lose something: either the collateral (as in a mortgage), or low interest payments (if you become a "bad risk"), or the right to borrow at all (if you declare bankruptcy, you will have trouble borrowing for 7 years).
The lender is also making a calculated bet. If they ask for collateral, their risk is lower, and they will charge less interest. If they lend you money without collateral (eg a credit card), the interest will be higher. The very fact that unsecured loans charge higher rates means that the lender expects, on average, to make a profit, because the higher interest will make up for the occasional default.
There is no personal relationship between lender and borrower. There is no moral obligation. It's just business and probabilities.
Unfortunately, people confound the two kinds of obligations, personal and financial. Lenders benefit from this confusion, because borrowers will have trouble being cold-blooded about the agreement they are entering into.