Tesla's, until quite recently. It's also fantastic for tipping people online without all the grossness of Patreon or Medium. Easier than making a wire transfer (my bank sucks). I tend to use it everywhere I used PayPal, minus the places where it isn't supported.
Exchanging cash for cryptocurrency without a bank inbetween is a pain in the ass, but its a hell of a lot cheaper than, for example, Western Union.
I live in Mexico, I don't know if we're first world or not. We're kind of in between. We have bank accounts and debit cards here too. In the past when I wanted to send cash to the US or vice versa, I've used Western Union for the convenience - the local corner store (which in Mexico will be Oxxo or 711) has western union. When my family here in MX needs money, I just transfer it to their bank account via my bank's app.
I think many people in the US overestimate how privileged they are compared to most of the rest of the world, to be honest. I lived in the US when I was young but left because life felt easier here in MX.
Sorry for this kind of ambling response, I don't really disagree with anything you said, your perspective just piqued my interest :)
By sending an envelope with cash. Services often offer that option. No E-mail or name disclosure required.
A few advantages: Your payment isn't traceable for all eternity for the whole world to see. The amount I pay isn't suddenly worth 10% more or less the next day. Better for the environment.