IMO the issue isn't discovery and research, it's development. Unless companies foresee a good return for buying/licensing/etc rights to treatments, discovered drugs with potential just sit there.

What sucks is when drugs are deliberately not brought to market, but kept in portfolios, because it might impact sales of other existing cashcows. For example, Gilead has a history of staggering the release of new drugs only once their patents expire for similar drugs they already have on the market.