People have legitimate reasons to avoid messing with BTC or others. Some people don't even want to hassle with currencies beyond their own.
Even if they oblige in accepting BTC and just convert it to their preferred currency, they'd be forced to go through the process of signing up and verifying with some sort of exchange. What if they don't want to do business with those institutions, or share their financial details to yet another third-party? Cryptocurrencies will succeed, thankfully, but some people don't want to put their toes in those legal waters yet. They will also have to spend more time administering to local laws and taxes regarding donations, which eats away the time they have for other much more fun things.
Even if they oblige in accepting BTC and just convert it to their preferred currency, they'd be forced to go through the process of signing up and verifying with some sort of exchange. What if they don't want to do business with those institutions, or share their financial details to yet another third-party? Cryptocurrencies will succeed, thankfully, but some people don't want to put their toes in those legal waters yet. They will also have to spend more time administering to local laws and taxes regarding donations, which eats away the time they have for other much more fun things.