Just gonna disagree with you there. When you are really big, women do comment on it like 90%+ of the time. My guess is that if the girl says nothing, that's an indicative that she's had bigger (so no need to ask lol).
Or they dont really care too much about it. Some girls dont really take too much notice of size. Or they dont want to be seen as either inexperienced or like they have slept with lots of guys so keep quet about the size.
I had one partner who I found out over a year later that she got shocked and super nervous when she saw my size. First night not a word about it though. We were together for almost 3 years and for the first 6 months my size never came up. In the last 6 months it did almost every time we had sex and even now, years later, she mentions it. But if we had only had sex a few times I would never have known what she thought about it. Lots of reasons to never say anything even if they notice.
Another serious partner didnt really connect the dots and that my size is huge because I am 195cm tall and her ex who also were rather hung was like 165cm. If we only compare our dicks to our bodies we would probably look the same size. It wasnt until the light were on and she had it on her face sober she really realized I am way bigger than her ex.
They dont have to have had bigger for no obvious comment.