Those are already challenges the USPS has to deal with. They have infrastructure in place to address those challenges. If they're paying those costs anyway, they might as well add services that can take advantage of that investment in exchange for more revenue.

There certainly would be an additional marginal cost, but it would be much, much less than an entity trying to start that from zero.

I believe something like 10% of NYC is unbanked.

Of hand, I believe it is a lot higher than that. I listen to an NPR (Or was it NYTimes?) podcast that interviewed working poor people and the number thrown around was that something like 40% of Americans working poor are unbanked with some areas of the country upwards of 60% (I think they said certain zip codes in Queens) are unbanked. What really stings working poor people from using banks are the hidden fees. There needs to be cheap and no frills banking for the poor.

Banks are required to offer such accounts by law in NY:

https://www.dfs.ny.gov/consumers/banking_money/basic_bank_ac...

Do you mean even cheaper and less frills than that?

It's not for lack of banking locations.