Let's walk through this. Drug develop is mostly funded with private money. Yes, the NIH funds basic research that often support drug research, but private companies fund most of the bill. It's in the hundreds of billions each year.
Now why would they do that? Well, they expect that they'll give a company $500M and it will turn into $2B or $3B. However, most of those companies will fail and the $500M will turn into $0.
So that would mean that the returns on the drugs that are successful need to be really high. What if they weren't? Well, all that private money would dry up pretty dam quickly.
Look at the money going into cancer research. It's a huge amount every year. It's not just because cancer is a terrible disease and affects everyone, it's because the returns on cancer therapy are high.
You could just tell private companies, "stuff it, you don't get to make money" and try and have the gov't do it on their own. Of course you'd need to increase the NIH budget by what? 10x?
Our current system isn't perfect, but it does a dam good job aligning the incentives of people with money and people who need new drugs.