Purely adoption, and there are a lot of barriers in the way. All we need for bitcoin to grow is for people to actually keep on using it and for others to get on board. Doesn't matter whether it's for an investment, currency or whatever, we just need people transacting their fiat for it, but things like fud, and regulations, and crashes and panic in the media scare a lot of people away. As for how we can change that, well I guess just educating people, but the general public probably won't really listen but we can certainly keep doing our part at trying to educate people and fix that, but it won't be easy.