You wouldn't be able to receive a salary without a bank account.
This is untrue. At least in the us, the company is required to cut you a check, which can be cashed without an account.
This, in itself is another issue, and should not be the case.
Banks fail, and no one should be forced to need one.
Perhaps they are a self-employed mobile pharmacist.
Europe is not America, and they generally provide better services to their poor people. Someone else above pointed out a certain country has onramps into banking explicitly for homeless people.
The people I know going around spending cash for large purchases tend to not be people that are struggling. They just prefer using cash. It doesn't get any simpler than using cash.