I'm too young for medicare, but when I asked my dr. to prescribe the heart scan, he kept stalling. When I followed up, he said my insurance wouldn't pay for it. Then I checked into pricing and it was $130 lol. If I have a family history, why would he assume I didn't want to pay the $130? I later found out that the his medical practice gets penalized by the insurance company for recommending "too many tests." So that plays into it.
I once tried to get some pills at CVS. I was charged something like $500, and asked for my insurance information. When I told them I had no insurance, they told me to go talk to a person a few meters away so that he can help me... I got the pills for $30.
If you want a CAC scan you can just go directly to an imaging center that offers it and order it yourself. It doesn't require a prescription. In most cases it won't be covered by insurance for screening purposes.