Especially here in the Asian developing world, you will find large informal economies. There is strong resistance against paying and getting paid through the banks. There is strong resistance against keeping money in bank accounts. People prefer to save in gold.
People do not want to trust third parties with their money. They distrust that concept. On top of that, these third-world countries have imported KYC/AML rules from abroad: Know Your Customer/Anti Money Laundry. People already did not want to use the banks, and these obnoxious policies only make the situation worse.
People sense that formalizing the economy is dangerous, because government taxation is dangerous in thirld-world countries. International financial organizations lend them 10 billion for a 10-million hospital project. These international financial organizations collude with local politicians to massively inflate the bill. Inclusive of usurious interest, the third-world country will end up paying back 20 billion, collected as taxes on the population. The only thing somewhat putting a stop to this scam, is the fact that the third-world country is not able to collect enough taxes from its population in order to pay the bogus bills. Therefore, the fact that their economy remains largely informal, spares them from getting ripped off spectacularly.
Some import bills can really not be avoided, for example: oil and gas. Economic progress also requires to expand international trade. There is a risk, however, that the expansion of international trade will drag them into the fiat banking quagmire. Until recently, the only realistic way to pay and collect invoices from abroad, was through the fiat banking system. Unfortunately, that meant: dealing with the hated fiat bankers.
Nowadays, it has become possible for third-world countries to expand their international trade without selling out. They can settle their international bills with bitcoin. In that way they can avoid to fall into the trap of creating a formal economy that will turn them into taxation slaves of foreign financial cartels.