You missed the "because", see my other answer.

I don't doubt, however, that being really thick-skinned is a necessary trait for surviving in that business. Soft-hearted types also don't last long as drug dealers, surprisingly.

My point is that a theory that says their business practices follow from moral failings doesn't explain anything about the world. Some businesses just mysteriously seem to always be run by bad people.

Conversely, assuming that every businessman is about equally greedy forces you to look elsewhere. Their loans are almost by definition high-risk, that's why they are expensive. Low-risk borrowers are a different market.

The fact that we can learn something by thinking about their business does not mean anything like "defending". It's just that sometimes the lessons are clearest with extreme examples. We can learn interesting things from studying drug gangs, pirates, kidnapping schemes, too.

We can also ask questions about whether the world would be made better by prohibiting loansharking, and I actually don't know enough to have an opinion. But it's clear to many that prohibiting drug-dealing has had some nasty side-effects.

So why doesn’t one of these greedy lenders steal market share by writing payday loans at closer to normal rates?

Well, are you really claiming that the cause of high interest rates on payday loans is poor morals? Unusual greed? Which mysteriously descends on all who enter the trade, every time?

That's the whole reason I used the example of loansharks, as I thought everyone understood by now that even if the angels ran that trade, such loans would be very expensive. But see below for other arguments against this bad-morals argument.

I've never seen numbers, but given the abundance of competing outfits, I'd expect that it looks roughly like any other business, once you account for all the costs. It could be a little more profitable if distaste drives some potential competitors to stay out. It also seems like a great front business for laundering, but I wouldn't guess that's a large proportion.