I cannot speak to why, but I do know that TRT+HCG was not good enough for me. My TT was around 1000 at the time and FT 36. Those are very good numbers, perhaps excessive, but still I did not feel right in many ways.
When 1mg/wk of arimidex/anastrozole was added to the mix, my libido and performance went from "what" to "WOW!". Sensitivity, sensation, harness and duration were all greatly improved. My E lowered from 37 [not really high] to 22. There was a change of FT:E. And my mood and other things, like mental clarity, also improved a lot. Of course everyone is different, but one cannot tell in advance on how one will respond to such interventions. Only one person will know when it works right.... you, and your blood work does not indicate that you should have certain problems or that AI will be a magic bullet. But many are starting to think that that is the way of things.