People are used to using traditional currencies to pay, and in my opinion it will take a long time for people to start using bitcoin as payment for medical services. Perhaps private clinics will start using bitcoin before the state. I think the main reason is the instability of the bitcoin price.
Not at all. Most probably it's about lack of knowledge.
The volatility doesn't matter, since the price is fixed in local currency, you pay at the spot price of Bitcoin and the payment processor does the conversion. The service provider (or seller) will receive local currency as always.
In my country there is one payment processor that accepts Bitcoin and it's slowly expanding. At first there were a few online shops where Bitcoin payment was accepted, now there are also car vendors that "accept Bitcoin" with this same method. So it is possible for any service provider and for them there's not much of a difference if you pay in Bitcoin or you pay with your credit card.
