Medicare didn't cover drugs at all until 2003 when Bush put together Medicare Part D to bolster flagging support. Medicaid doesn't negotiate prices either, but it's mandate that it will pay the lowest negotiated price in the market. When Part D was passed it almost had a similar structure. In 2016 there was a move to add negotiation but it fizzled. In both cases the CBO estimated that negotiating prices would save precisely no money. The way Medicare plans actually work is that plan provider bid to be part of the program and they are selected on a cost basis, and they then negotiate drug prices. Could Medicare administrators do a better job? Well the CBO has twice said no. Medicare Part D was a huge hack to cover a made up problem, which is to say seniors too wealthy for Medicaid not being able to afford their heart medicine. It was essentially GWB trying to buy voted before the 2004 election. So I think you're wrong on the history here.