ruveyn wrote:
On loans you pay interest on a diminishing principal balance.
Not necessarily. If you can't cover the interest in each payment, then it's exponential. The less you are able to afford it, the more you will pay. In this way, interest can become an exploitation of poverty itself, directly.
This can happen through no fault of the borrower (or lender), for instance if a person suffers an injury on the job and can no longer work.
Not that I am saying we should forbid charging interest on loans, but we can make rules to avoid or mitigate situations like this, which can be dangerous for both parties as well as third parties and society as a whole.