> If there was zero risk there should be zero premium.
Suppose someone living the HN dream makes a bunch of money from his startup, and decides to pay off his mortgage. It might be structured as a loan from his company to himself, which then has zero risk.
A bank processing an FHA loan has zero default risk, since the government steps in to pay them. And they often sell the loans to a government-run company anyways.
A bank giving a conventional mortgage will often require 20% down, and again they resell the loans to a government-run corporation after a few years anyways. If you default in those first few years, they effectively get a 20% discount on the original purchase price of the house when they take it. Not zero-risk, but the 2008 financial crisis appears to have only had a 30% drop in house prices. (Obviously, subprime lenders can't resell their loans to the government, and didn't require a heavy down payment)
Generally speaking, the idea that interest mostly pays for risk assumes that there is no 'low-hanging fruit' where guaranteed returns are possible if only there was money. Paying down high-interest debt is one form of guaranteed return, so theoretically there shouldn't be such a thing as high-interest debt if the market was mostly efficient.
I guess the conclusion of your view is that: If people were more diligent about handling their money, banks wouldn't make as much risk-free money.