For bitcoin to work as an effective currency, it needs to be stable. The reason why there aren't that many merchants around the bitcoin ecosystem is because they are scared to receive a payment that's too volatile. Bitcoin would have been an excellent currency since you can use it across borders without having to exchange to a country's local currency just to buy something, so there's that.
I rally doubt that statement. Bitcoin was never a stable currency since its inception in 2009. Did this volatility hinder the growth of it? Absolutely no! The volatility is not a reason. The reason is its legal status. Bitcoin is not legal in majority of the countries and the merchants are usually a legal entity. So they just don't want to get into something which doesn't have a legal status or the legal status is confusing. That is the main reason for not accepting bitcoin by many merchants, not the volatility! It's just an excuse.