A currency should be much more reliable so people can trust their money or even saving with it.
Bitcoin still has a long way to go before mass adoption.
I've been saying this for a long time. If people want bitcoin to be a viable currency, it needs to be a stable store of value. Rapidly appreciating and depreciating makes it useless as a currency because the longer you hold it, the less certain you can be what your holding is worth. It's a catch-22 though, because people only become interested in it when the price is rising, and people who are getting in to speculate are hurting the cause long term by contributing to volatility.