Imagine when people paying for a certain product, and the display price of BTC changes every time he walks into the store. In this case, I think people will not feel comfortable with BTC until the price is stable.
People will be comforable with bitcoin when it is now more trending all over the world, right now i can say that there only few people are comfortable using bitcoin because it is not still known in all countries but when it's already known for sure people will really support it.