Disposable diapers are a luxury item. Buy cloth and reuse them a hundred times. I could afford disposable and still bought cloth to save a literal crap ton of money.
Cloth diapers are a luxury item. They are for people with access to washing machines and sufficient time to handle them. They might financially seem cheaper, but poor people often need to work multiple jobs to keep their heads above the water. They can’t afford spending extra time. (Same goes for junk food vs. cooking stuff that you cheaply sourced from a market, ...)
I believe people in developing countries without access to washing machines use cloth diapers, so it’s not lack of access to washing machines. Cultural issues probably pay a role, however.
We bought ours on eBay (third hand, and they did for 3 kids and still were good enough to sell on), they were more work than disposable but certainly cheaper. But, we had a washing machine -- again, second hand (fixed and plumbed in by me).