The model may have predictive value in a population without explaining or predicting a particular individual's cancer. After all, breast cancer existed before abortion became so prevalent; there is an underlying rate of these cancers within our populations. It is also possible that all the women you know who have had breast cancer haven't told you their abortion histories. It's not a typical topic of conversation, at least among my women friends. Statistically, I'm sure I know women who have had abortions, but I've never had a conversation where it's been admitted to me.
This article does not say that every woman who has breast cancer had an abortion. It does say, however, that having an abortion greatly increases a woman’s risk of getting breast cancer.
If we know that abortion is a cancer risk factor, shouldn’t women be made aware of that fact? If we can lower the incidence of breast cancer by decreasing the number of abortions, isn’t that a good thing?
By that logic smoking is not bad for you because many smokers do not get lung cancer. But there is a correlation.