I asked my doctor the same question, I had no interest on going on birth control if I didn't *need* to. According to my Dr. it's not medically necessary, only if you want to deal with symptoms of high testosterone levels like extra facial and body hair.

PCOS sometimes comes with high androgens (levels of male horomones). If you have those issues and get on BC, they will probably improve symptoms. For me, BC makes my hair thicker, completely takes "period" pain away, and prevents pregnancy. So I like being on it, at least for now.

There are a lot of rumors about BC and its link to lower insulin resistance. If those rumors are true, then BCs could actually worsen the underlying condition of PCOS. However, I've seen studies published saying that BC doesn't affect insulin resistance, and I've seen studies suggesting that they do. It's one of those things that, in my opinion, will be much more clear in about a decade or so (hopefully).

In short, I think you have a smart doc who is more concerned about long term effects of BC on your PCOS. If you're not looking to prevent pregnancy, I think it's wise to stay off them just in case.