It is great to buy things with bitcoin but many merchants are just negative to accept bitcoin due to its volatility. During the last great price drop from 20k$ to 6k$ many merchants have suffered from huge losses due to the price drop. And that is why the number or merchants have decreased and even huge businesses online have started to decline the use of bitcoin due to their losses.
It's because of the volatility that's why they are so reluctant to accept it as payment methods and i believe that it is going to be resolved in due time since it's a very new market and maybe some regulation will help with it's volatility as well.