No, every woman does not get it. Many, many adverse side effects. Many risks.
You are correct; almost every sexually active woman has used a form of birth control, but that doesn’t mean they continue to do so constantly; and the bill is the most often used, but it isn’t the majority. Sterilization is a close second, but note that you do that once, while each year there could be a different set of women taking the pill.
About 10 million women are on the pill at any particular point in time.
And of those, about 1.4 million do so for medical reasons unrelated to contraception.