They're a business not a charity and they still have the same operational costs (staff, equipment, systems, compliance, debt recovery) as those who lend far higher amounts of money at lower APRs.
Yes, the APR looks scary, but they're a lot better than the alternative for people who can't get mainstream credit.
For example, they sell a washing machine for £260 that you can pay for at £9 ish per week for 32 weeks and yes, it does cost nearly £300 over time and that's more than better off people who'd just go and buy one without thinking would pay, but they're a huge amount better than the likes of Provident, or Bright House, where you'd probably end up paying more like £500.
Plus yes, they have the Iceland microloan scheme, which is admittedly likely a loss leader for their main credit business, but used wisely, for essentials, I think on balance it's a good thing they're doing. And they report to credit reference agencies, so build good credit histories, which can help people access 0% finance and credit cards, so they don't need to use this sort of company.
And of course we have to treat people like adults, in charge of their own decisions, so while a minority might use the service to buy things they don't need and can't afford, we can't restrict what people can or can't buy or the range of goods that a private company sells, providing they're not illegal.