I think your question should be "Why other business and companies still doesn't adopted bitcoin?" Because there are business and companies that already are using bitcoin as their primary payment and accepting it as payment, And if you are not aware of it now you already know, But why do other business, establishment, and companies still doesn't adopt bitcoin, I guess there are still people that doesn't trust bitcoin or other Cryptocurrencies, Or they don't have enough knowledge regarding it and may have a mind set of a risk regarding the unknown.