Comment by Jiro

The system doesn't know that you're a smart person who will only say "I have a regular cycle" when you've had something that could reasonably be called a regular cycle. A lot of patients are stupid, and requiring a quantitative answer eliminates one source of stupidity. Yeah, this particular doctor knows you're smart, but I hope you can see what disasters might result if the procedure said "the doctor may skip this step if the patient is smart".

It's the same reason why the doctor will take your temperature, instead of accepting your word that you took your own temperature and it is normal.

https://www.who.int/publications/m/item/primary-care-checkli...