Is it that odd to think that there are well funded big pharma interests in making sure that only that which is patented is approved?
Sadly, most of the proof that treatments work are provided by the drug company that has a profit motive to produce that proof. There is no interest in providing that research for something that isn't controlled for someone's profit.
To be clear, there's nothing wrong at all with profiting from research done. It's also very important to understand the risks taken when using something that isn't well studied. Natural doesn't mean safe, of course that's true.
But it also isn't a conspiracy theory to say that people who have billions of dollars in profit at stake may occasionally give money to the right Senator, or fund only that which is in their interest.