Legacy currencies aren't infallible and can leave a lot to be desired. Many, if not most countries have suffered through currency crises, high inflation, devaluation or capital controls. Bitcoin and digital currencies could potentially be an improvement over existing currencies in these situations. In addition, it it were possible to do business with anyone around the world using a common currency, that would seem to be an ease of use and efficiency improvement over the status quo.
Of course, for these things to happen, a digital currency would need to grow large enough to become stable. That's a pretty significant chicken and egg problem. The Bitcoin market cap has grown to about $4B, so there are certainly plenty of people experimenting with it, including some prominent startups and VCs. It may take a while to achieve critical mass, but I think it does stand a chance of happening.