The biggest issue is the volatility and I think that's what scares a lot of people off, but at the same time its that volatility that is very attractive to speculators and thus the potential for profit. For the average user who may wish to use it as a currency though it can be scary for them.
This is what I thought for the first time Im doing trading bitcoin, I scare about the volatility but at last I think without any volatility I dont think I can get good profit. With this volatility we can earn every time and get much profit from it
But the opposite is also true. You can lose a lot of money and profit not at all. Trading or investments always carry risks and are not always profitable.