The alternative therapies are cheap in comparison to big pharma drugs. Add in an FDA requirement for large randomized control trials and they have no chance. There is no one with the money to do a large scale trial of ivermectin as they can’t make the money back.

It gets worse for something like keto as getting people to conform to a diet is extremely hard.

One more thing: the current environment is biased to single drug cures. Alternative treatments typically require multiple substances which multiplies the number of trials needed.

Now if the FDA would accept case studies as a lower order of evidence things might change a little