They actually use crypto. But of course it's a more complicated way to donate. With services like "By me a coffee" it's a matter of several clicks, when with crypto the donator is required to actually understand the whole flow. So, it's not the best UX when we talk about donation links.

The problem is the same. It still costs money to support crypto payments via taxes, payment fees, customer support etc that it's not worth to collect crypto from these countries. It's much more lucrative to just target US markets

Because no one wants to use a currency that is tightly (and correctly) associated with child porn and North Korean scammers.

I used to see the occasional crypto donation link, and you can still find several websites for companies offering to facilitate that, but I haven't seen one of those links in a long while.