Most of them mention a range of scores. China and India use scores which by themselves give about 3 billion people with credit scores based on statistical modeling.

A lack of cash flow is a lack of financial history which makes one less predictable and therefore riskier which lowers your score.

They want an established history showing you pay things you've agreed to pay. I've never made a lot of income, but I've always paid my bills on time, so even with a smaller cash flow I still have great records of always making sure I have enough to pay what I'm expected to pay, so I'm seen as reliable to any possible debtors.

Not unique to the US, we have the same thing here in Canada