*****Because Ivermectin by itself just isn’t effective******
No drug is 100% effective.
Again, here are 63 studies that show it is at least 86% effective as a prophylactic and 70% effective in early treatment.
https://ivmmeta.com/
If it wasn’t effective, Pfizer and Merck wouldn’t be duplicating it in their new pill.
They're not...and you should spend more time reading your own links