Forcing people to have a bank account or a credit card to buy food enforces a monopoly on money.
And allowing businesses to not accept cash allows them to streamline operations and offering products/services at a lower price.
What does monopoly on money mean? Why didn’t Washington DC go out and invest in infrastructure to take cash from people and give them debit cards?
Because that would leave the politicians more liable and the costs are easily visible. Much easier for them to punt the responsibility and costs to a small portion of the voting populace.
If no such business exists, it is because the cost of the risk/hassle of dealing in cash is too high compared to the low market demand.
Like, if enough people want handjobs from non-sex-trafficked sex workers, surely some massage parlors will open to cater to ethical customers, right?
Markets do not guarantee civil rights, and they shouldn't be relied upon to do so. Moreover, their failure to do so should not be construed as a proof that broad enforcement of those rights would not improve both individual businesses and the wider economy. Nor should the economic impact be the sole reason for society to choose whether those rights are worth defending.
By your logic, businesses can choose to refuse service on the basis of race because a certain race is poorer on average - and people from that race just have to hope they will be served by another business that comes along to hoover up their money.
We as a civilization have decided that we don't want the market or a collection of individual businesses to make those sorts of decisions. Protecting people from predatory discrimination is the role of civil society and government, and why we make businesses conform to certain standards, whether they like it or not.
The answer to people being unbanked is to make banking easier and less discriminatory. Not to force everybody to accept cash.
I hate this argument that "someone will start business"
No. If people will struggle with getting food then they will adjust and get cards despite not liking it. Nobody will open business for them.
For me this is some kind of free markets naivety
Why do countries print currency? For the settlement of debts public and private. It's not merely a civil rights issue. It's a core governmental function to provide a public and universally accepted instrument of trade. Governments which partner with privately run banks and coerce citizens into using those banks are inherently corrupt.