Because there's no money to be made with a very cheap generic drug.
If Ivermectin had been proved to be an effective treatment, the emergency authorizations wouldn't have been granted to the vaccines.

"“every time we mention ivermectin, we get put in Facebook jail.”"

Facebook seems like a funny place to publish drug trial results. How about medical journals? What's Kory's track record there? Anyone done an overview of rigorous clinical trials of the use ivermectin on covid victims?