I am not sure how to answer your question about WHY doctors put women with PCOS on injectibles. However, I do know that women with PCOS who do injectibles have been very successful.
Unfortunately for me, I did injectibles (75ml) and I DID NOT overstimulate, However, I did not get pregnant either. So, I guess I was just unlucky on my first try at getting pregnant. But was pleased my cycle was not cancelled. Our insurance did not cover it, either. It is really difficult that is why we have taken a 2- month break. If I don't get pregnant by September, then I will do injectibles again.
I hope this helps and good luck. Remember that while on injectibles, they monitor you VERY closely and can adjust your dosage along the way.
Good luck to you!!!!
Pam