If you have a chain of A owing B $2k/mo and B owing C $2k/mo and so on from A to Z, then if A through Y's sectors all change, Y still needs to pay Z, meaning X needs to pay Y, mean W still needs to pay X, and so forth. Meaning that even though nobody's paying usury rates, nearly everyone is still heavily constrained in terms of how they can adapt to change. And so they're incentivized to push the world towards whatever scenario they planned for, not because they like that scenario a priori, but because that's what they planned for.
tl;dr Credit lets you play time arbitrage, which sets up bad incentives when things don't go according to plan.
We shouldn't have chains of people owing money to each other, we've seen what happened in 2008. Prohibiting lending money with interest will not allow such chains to form.