President Roosevelt passed Social Security because over 50% of the elderly were living in poverty and the program worked well, lowering that percentage to under 10%. President Johnson passed Medicare/Medicaid because too many of the elderly and poor couldn't afford health care -- and now all of the elderly and some of the poor have health insurance. President Obama passed the Affordable Care Act to fix the inequities imposed on consumers by insurance companies and to cover more people with health insurance -- and it will do both (except in those states where the GOP refuses to expand Medicaid).
The Republican Party has opposed all of these programs. They are still trying to privatize Social Security, eliminate Medicare/Medicaid, and defund/repeal Obamacare. Why do they do this? Because they are the party that represents rich people and corporations -- and rich people and corporations don't need Social Security, Medicare/Medicaid, or Obamacare. Those programs are only needed by the bottom 90% of Americans (the people the Republicans don't care about).