Bitcoin is at the very beginning of it's rise to mainstream use. it's going to be volatile.  Merchants can just use services like bitpay which removes volatility risk for 1% with no minimum transaction size.  You can't expect a revolutionary innovation in currency thats only been ou a few years that has only a fraction of major fiat currencies to be just as stable.

There is going to be a few years of exponential growth and volatility, until trading volume is sufficient and market cap is large enough BTC at $10,000-$100,000.  Then volatility will be more akin to that of major fiat currencies, perhaps even less.