The Ghost Foundation is a UK organisation and I can assure you that USD is not the default currency here. If they're willing to make the effort to accept USD, I'm sure there are plenty of bloggers able to make the effort to pay using it.

Regardless, USD is the de facto standard for SAAS payments (whether this is good or bad is a discussion for another time). If you can't pay in USD then you'll find a substantial proportion of services unavailable to you.