In France (and probably in other European countries), private health insurances from employers are complementary to the government health care and don't replace it. That's why it is much cheaper. And so even highly paid professionals still use the government paid health care. Moreover, if it wasn't the case it would make the national health care system a lot less efficient.

At least in Poland, the private health insure won’t cover serious procedures, eg they will cover cardiologists, but not a hospital stay, operations, etc. this means they are much cheaper because they don’t have this tail end, high value risk. You still rely on the national insurance and health care system for that.

What countries is this true.

I know zero people who have private health insurance. Some companies offer it as a perk, but I have never heard of anyone paying for their own private health insurance.

Ireland. Without private health insurance you would be waiting many years before you would get to see a consultant in the public system. To even get an appointment in a public hospital in a reasonable amount of time you need private health insurance.