Bitcoin price goes up and down all the time. If someone buys something costing 10$, the next day it may cost less or more. So it's a risk for the seller.
this is a topic that is discussed every year and I believe that most people would be satisfied if bitcoin were accepted as a means of payment and all countries in the world. But breaking the barrier of high volatility won't be easy anytime soon because in this crypto market people enter with the hope of making a lot of money and there are whales that focus on manipulating the price to make a lot of money. Imagine the trader who loses 40% in just one day because the bitcoin price dropped 40% in just one day because some whale manipulated the price? it really is a pitiful situation