My wife is an Ob/Gyn, subspecializing in reproductive endocrinology (i.e., an infertility doc). I asked her about pelvic exams as a prerequisite for birth control pills.
She said there really wasn’t any medical reason to require a pelvic exam before prescribing the Pill, and she did not require it of her patients. Now, this was an offhand response to a question I asked when we were both in the middle of something else, so I’m sure she spared me a lot of nuance and edge cases. But, in general at least, a pelvic exam is not medically required before getting birth control pills. (I assume the answer is different for IUDs. I would imagine you’d need a pelvic exam before implanting a foreign object in your uterus. But I didn’t ask that.)
My wife said that some doctors require a pelvic exam anyway. Some do it, as someone suggested upthread, to pressure patients into getting their yearly pelvic exam. While my wife agrees that yearly PEs are great and all, she doesn’t want to erect unnecessary barriers to women who want birth control. My wife stated it as, the cost to the patient and society of unwanted pregnancy is so high that it outweighs the benefit of the PE, so using birth control as leverage to get the patient to have the PE seems wrongheaded to her.
She also said that some doctors require a PE so they can get more revenue for the visit. The patient is in the office anyway, might as well as ring up the PE. Yay for profit-driven healthcare. My wife is an old fashioned sort who thinks you should do what’s best for the patient even if you lose a few bucks. Luckily she works at an academic medical center, which is only mostly, but not entirely, driven by the profit motive.