This is qa falacious point. "even though they never put money in to fund that particular benefit. There is no putting in to these paygo programs. Current taxes pay current benefits.
The argument around SS is that if you pay in you get benefits. The drug benefit was something additional that was never accounted for in the SS/Medicare withholdings. I understand that the way it really works is that current taxes pay current benefits but that's more of a function in how the government chose to manage those tax receipts.