A good example of a company doing that is Zendesk: as an engineer, I want to make a comment on a support ticket once every 3-6 months, but Zendesk would require my company to pay for another user license to do that. That's not value provided nor is there a cost for them in having another non-read-only account. They are attempting to rob their customers instead.

I don't see how that is possible.

(1) Keyri private keys cannot be stolen other than through smartphone malware, which is exceedingly rare, while password managers and older USB keys are vulnerable to desktop malware, which is much more common - both credential stealers and, in the case of older generations of Yubikeys, keyloggers. Hardware OTP devices are additionally vulnerable man-in-the-middle phishing attacks (though the HN audience is generally savvy enough to not fall for phishing) - https://github.com/kgretzky/evilginx2.

(2) As long as you rely on passwords and TOTP, you're relying on the shared secret paradigm and trusting the relying party to handle your credentials properly. If the relying party's credential store is breached and the credentials were improperly stored (common even today), your credentials (both your password and OTP secrets) can be used by a bad actor to access your account. Public key systems like Keyri and FIDO2 substantially reduce this risk.

> As I said in a comment below, the fact that companies "can afford" is not the same as "it's worth it" to them

Please see my response below regarding account sharing. In short, eliminating account sharing in order to enforce TOS is an opportunity to (a) improve security (b) improve UX in cases where provisioning multiple users access to one account is warranted.

> Finally, with OpenID, I can set up my own identity provider, or use a privacy conscious one.

As you note, the vast majority of web services don't support arbitrary identity providers or use privacy conscious ones. History has proven that people don't set up their own identity provider. Additionally, the universe of "privacy conscious" OIDC providers is limited (non-existent?).