I think most users repay the loan soon after obtaining it. The rates of interest are high but not punitive on a very short term but are set high because of defaulters and that the company wouldn't make much at an annual 3% or so for a week. And, no, warnings about debt won't deter the public who are minded to use the service.
Mind, the more prosperous may use the service because banks are so brainless. I asked for a £1,000 'facility' for two weeks. This enquiry was transferred to some credit department which asked for a full statement of my assets and liabilities and that meet with a manager. Intrigued, I met her. She refused the money because I didn't fit the bank's criteria viz. I didn't have a regular monthly income. Now, I have 20 employees. I asked whether they fitted the criteria. Yes , they did, she said. "So they do, but the bloke who pays them their regular monthly wage doesn't?" I asked. She replied that she saw what I meant but the answer was still no because I didn't fit the criteria!