there are a lot of reasons that people are not accepting bitcoin as payment and being decentralized is not one of them.
here are some of those reasons:
1. lack of customers willing to spend bitcoin. there may be a lot of bitcoin investors but only a small percentage of them are spending it.
2. high fees. which may be temporary now but that throws people off.
3. high volatility. unless you are converting back to fiat immediately or believe in the future of bitcoin, it is tough to accept a volatile currency.