Medicare supplement plans and Medicare Advantage plans were developed for a very simple reason. Medicare does not provide 100% coverage for health care services and does not cover some services at all. Medicare is a creature of the early 1960's and people over age 65 at that time on average only had several more years of life expectancy plus there was a lot less that the health care system could do for people back then. These factors have changed significantly 50 years later with seniors living longer, more active lives and with a multitude of medical and pharmaceutical treatments available to them.
If you are becoming eligible for Medicare today, there is a very good chance that over the remainder of your life you will have multiple opportunities to utilize services under Medicare for which you will have to share financial responsibility (e.g. - hospitalizations) and it is almost impossible to become a senior citizen in America these days and not be on one or more prescription medications (prescription coverage for seniors on Medicare didn't even really exist until Medicare Part D was created by the Bush Administration in 2003). It is to protect yourself against these out-of-pocket expenses that people purchase Medicare supplemental coverage that fills in most of the gaps in Medicare's coverage.
If you are becoming eligible for Medicare today, there is a very good chance that over the remainder of your life you will have multiple opportunities to utilize services under Medicare for which you will have to share financial responsibility (e.g. - hospitalizations) and it is almost impossible to become a senior citizen in America these days and not be on one or more prescription medications (prescription coverage for seniors on Medicare didn't even really exist until Medicare Part D was created by the Bush Administration in 2003). It is to protect yourself against these out-of-pocket expenses that people purchase Medicare supplemental coverage that fills in most of the gaps in Medicare's coverage.