Thats not the case in Canada for example ( and if I have this incorrect would some Canadian please correct me).
In Canada you can buy suplimental insurance to cover things not covered by the natioanl plan, but you cannot buy private insurance that covers things the national plan covers.
And thats what Bernies Medicare for all does as well. Only suplimental plans since Medicare only covers 80% ( a point many who favor his plan know nothing about..all they hear is free)
Of course the goal here is to force eveyone into one system and to eliminate a perhaps better secondary market outside of MFA.
My wife and I are on Medicare. It pays 80% of their schedule rates for medical fees. We're responsible to pay the other 20%. But we have another private plan that we pay for that picks up where Medicare ends. We have co-pays on drugs.
We pay for Medicare. It's not free. Depending on your income it costs around $145 per person per month or $3500 per couple per year. That's minimum. Depending on income, it goes up from there. The premiums are deducted by the government from your Social Security check. So the idea Medicare is free, isn;t true even for the elderly who are covered. It also doesn;t cover doctors who have "opted out". If you want to see those doctors, you have to pay their higher fees fully on your own out-of-pocket. Neither Medicare nor your secondary insurance pays anything. So the better doctors are for the rich. Before we retired and went on Medicare, we had a private plan that covered all doctors. So if they create Medicare for all, many more doctors will opt out and people will have to use worse doctors. So our medical care will go down not up. Lower fees will also attract less qualified people to medicine so that will also reduce the quality of medical care.
Employee's salaries are taxed at 1.4% which is matched by their employer while you are working before you start to collect. So if you earn let's say $50,000 a year, you pay $700 and your employer pays an equal amount. If you earn a million a year, then you pay $14,000 and your employer contributes an equal $14,000. There's no top limit on Medicare deduction from salaries. A big time ball player who earns $10 million would pay $140,000 and his team employer would also contribute $140,000.