Let's turn the question around instead: why shouldn't banks be forced to behave as common carriers, at least when it comes to things like processing payments, providing checking accounts, and other such basic services? What good does it do to start a business, only to be told by the banking industry that you can't open a bank account for your perfectly legal business?

I'm not sure if I'd include lending in "basic services." That seems a bit more debatable to me.

I'd include lending in basic services. However it would tie it to pure risk, along with don't let a customer get into too much debt. Pure risk means you only get to look at risk from an actuarial/numbers perspective, nothing more. Too much debt I'm not quite sure how to word into proper legalise but that needs to be done before we can actually do this - maybe just better bankruptcy laws so that risk goes up too high before the customer has too much debt?

The sticking point in my mind for lending is that risk undoubtedly varies by industry. It's not really very sensible to force banks to lend money to businesses without considering what industry they're in. At that point, how do you differentiate a sensible underwriting decision from unfair discrimination?

Interest rate and documentation.

Pretend that a batch of YC startups are all getting loans rather than ownership purchases. What effective interest rate are they paying? What is the default rate where the startup dies before acquisition/profitability/IPO?

Write a heuristic to determine a fair interest rate given the current prevailing rates, financial history of the company in question, financial history of similar companies, and similar objective and quantifiable subjective factors. Document it. When someone complains, demonstrate to your regulator that your procedure was fair, reasonable, and applied evenhandedly, and to the extent possible is consistent with actual outcomes.

I'm not sure what you're getting at here. Any new batch of startups is so risky, I can't imagine a bank lending them a cent at any non-usurious interest rate until they've been in business for a few years.

Banks often do lend at better rates to companies run by executives with a good history.

Sure, but not without a personal guarantee from one or more of said executives, I would imagine. At that point, it's effectively the bank lending the money to the exec though, and not lending to the company.

That is the point. They should have numbers to show which industries get rates, and targets that a company meet (how is an open question - it might not be possible) to move to a different rate - either up or down.

There are no numbers for industries banks don't serve.

That leaves only illegal black markets where those involved avoid banks anyway because banks report activity to the local government. (illegal money laundering schemes do use banks, but there are numbers for banks to use even if they don't know about the illegal side of the business)

Once in a while there is a brand new industry, but they tend to start small enough that banks can figure out numbers before the risk is too big to worry about.

Lending and banking should be considered separate, if related business IMO. And bankers should absolutely be considered common carriers. Lenders should not.

Dutch banks terminated accounts of Corona-critics / anti-vax'ers / conspiracy nuts ( you choose how to call them ).

I wonder if climate change critics are next.

Dutch source : https://www.metronieuws.nl/in-het-nieuws/binnenland/2021/08/...

When I submitted it, I tried to find English sources, but couldn't.

Payment processors are heavily regulated by govts in the jurisdictions they operate in. They're not operating in isolation, rather they act as choke points for policy enforcement.