"There is little incentive for many pharmaceutical companies to develop cures for rare diseases"

Well, there are some. For example, if you find a cure for Wolfram's you might actually find a cure for diabetes at the same time. Some times looking at the extreme cases helps you zero in on the root cause. Not saying it's easy.

Also the gov does have additional incentives, otherwise no one would work on orphans: No one.

Regulatory Explainer: Everything You Need to Know About FDA’s Priority Review Vouchers
Posted 19 December 2017
http://www.raps.org/Regulatory-Focus/News/201...-Vouchers/

I do agree getting ODD these days doesn't move the needle on the sp. Although if you had a boat load to go alone with strong IP...