Why do we need a system based upon usury? We don't. Usury is an unnecessary and even harmful invention of the greedy, the predators, those who want to live off others without doing a decent share.
People must stop assuming that usury-based economics and banking are necessary. They aren't necessary at all. Lending at interest is not necessary. It's evil in fact.
For thousands of years, there was no interest. There were no blood suckers. People are so accustomed to it that they don't see it that way. Many work in the industry imagining that they are engaged in an industry that is not harmful but rather beneficial. It is not beneficial in the aggregate. It is rather a means by which some end up living higher and in luxury and even obscene and gaudy opulence while others literally starve. They chalk this up to survival of the fittest in the jungle that is capitalism. It's social and economic Darwinism rather than enlightened. It's dog-eat-dog rather than enlightened human beings taking care.