Medicare pays 80% of most medical expenses the remaining coverage can only be bought via for profit insurance companies.

Medicare pays 80% of most medical expenses and the other 20% of medical coverage can only be purchased at a higher monthly cost from private for profit insurers. Why not open up the new healthcare plan to allow those on Medicare the option to purchase their additional 20% of coverage directly from Medicare? Even if the Medicare purchase cost is identical to the for profit plan offerings then consumers have another option and Medicare should be able to retain this "profit" margin as a subsidy.