Exactly. It's not a "where do we draw the line" thing here, the line is already drawn as you allude to. It's not just CT scans as well, some actual medications need pregnancy tests or at least active contraception use. Roaccutane, methotrexate and other DMARDs etc - everything in medicine is a risk vs reward thing and I'm sure many patient would prefer not to be on a drug that messes up their fetus whether they're planning to keep it or not in the case they get pregnant. You'd rather just avoid the risk of that situation occuring altogether.