Simply put lawmakers are against cannabis regulation in large part due to the lobbying of Big Pharma. Marijuana had the potential to completely destroy the Big Pharma industry [due to effectiveness of cannabis], and therefore the entire US healthcare system. There is also the confusion of where to draw the line concerning recreational use and medicinal use, and how to incorporate it's usage into the existing regulatory framework. So for now, it is unfortunately still in the best financial interests of those involved in the current pharmaceutical ecosystem to limit and control access to marijuana. That being said, they really should take it off Schedule One Drugs.