The problem with Medicare in particular is that people collect vastly more in benefits than they ever payed into the system. That's why the Trust fund will run short of money to pay claims in 2028 if nothing is done to reform it.
In reality the money paid into the SS and Medicare system is already gone , the government has spent it and replaced it with an IOU. The government borrows a trillion dollars a year to make up the difference. That's just about exactly the same amount of money the government spends on Medicare/Medicaid every year. 
The current system is not sustainable and will collapse sooner or later if action is not taken to reform it. The current generation of retirees should be happy, they'll be  the last to receive the level of benefits currently paid out by medicare. Future retirees will get less to none depending on what actions are taken to reform the system.