The advantage of Western Union is that the person receiving the money be unbanked, living in a cash economy, and not even necessarily be literate, never mind technologically literate. To enable these people to receive and spend cryptocurrency there's a serious "last mile" problem that needs solving, and for everyone else there's usually already a better money transfer solution than Western Union, at least for legal transactions.

The developing world might have been impressively advanced adopting tangible digital goods like mobile phone minute allowances as transferable currency, but expecting liquid local markets in a highly volatile cryptographic tokens "mined" in foreign countries where mining rigs and cheap power are available seems like a big ask.