There is, in fact, a good reason for a donor to use Bitcoin over ACH. If the donor obtained his Bitcoin through shady means, or does not want to pay taxes on it

There is, in fact, a good reason for a donor to use Bitcoin over ACH. If the donor obtained his Bitcoin through shady means, or does not want to pay taxes on it, spending the Bitcoin directly can allow the donor to avoid disclosing his identity. Converting to dollars and using an ACH transfer requires associating the money with his real name and identity.