Why would they possibly not use ivermectin if it worked? The NHS reported that its anti-viral and anti- inflammatory properties were insufficiently robust to warrant any further study.
Plus various studies have shown that where it has any level of covid efficacy it's inconsistent, achievable only at significantly higher doses than normal and comes with a potential range of side effects, none of which is cited by its champions. Their fulsome singing of its praises is misleading, distorted, uninformed and highly selective.