The answer is that societies status quo is kept by communal agreement on right and wrong and punching down.
Sometimes it's surprise, and mouth before brain, but yes it's often being done to draw a hierarchical line in which you are forever judged as wrong or lower. You know when that's going on, and this was one of those occasions..
Don't be taking it.
In my day, myself, Mandy Smith, and Elvis's, and Jerry Lee Lewis's cousins where all seen as loose little Lolita's, and gym slip mums out to wreck men's lives as 13 and 14 yr olds, not helped by family involvement in passing us on. In R/L our legal guardians/husbands, baby fathers, were held up as virile men to be congratulated, and further bigged up for sticking around, marrying us and putting us to work, in and out of the house. We have a name for those men now.
Many joined a countdown to see a picture of Samantha Fox's breasts at 16. On my 16th birthday,I carried in my twin toddlers, baby, and visible bump to the magistrates court, old enough by hours to apply to get my marriage bans shortened. I was told how lucky I was that their father, my guardian, was prepared to "make an honest woman of me," and it was granted.
Of course his 'honor' or 'honesty' was never in question. Neither should any of it be expected to harm his life or reputation, disrupt his other hobbies, cost him money, or bring judgement on him.
Little point in putting miserable details on here about health care, schools etc, especially with the Daily Fail's love of shit spreading, but yes judged, and judged, and found wanting again, and again, and again. The younger you where, the more people like to look down in perpetuity. I paid so many times over for in retrospect, having had a life with few chances or choices, and sadly often in subtle ways, so did my children.
I ended up having to learn to fight back and take some authorities to court.
Many years later surprise! One (much loved) accident. Now I got judged again, as too old and 'haven't you finished with all that.' (Well evidently not!)
But then - we discovered homeschooling. Holey Moley, you think age gets you judged as a parent and a woman, based on everyone else's perceptions without facts?
Obviously everyone is also entitled to demand facts and then tell you they find them hard to believe! My younger adult children are seen as 'remarkable' for having taken up the careers they have with 'no proper schooling, and an underage parent. Obviously nothing I did was any sort of positive contributory factor. 
It's my female adult children, and grandchildren, never the males, that get the "oh you must have started young!" comments when we're all out and about together.
There's a certain degree of pleasure from mine turning round and saying " no it was her, actually" The perpetrators find it embarrassing when they've targeted the wrong female, which is interesting in itself.
Replies: In the past, I used to fall back on "That's a bit personal, isn't it?" with a jokey smile, and change the subject, when they demanded to know just how young I'd been.
At work: "The past is a foreign country for many,' and change the subject.
But if they where sniggerers or sneerers, : "Gosh, I don't think I've ever had a woman snigger before when asking that, it's usually men who do that" and subject change holding the upper hand.
Nowadays I think I'd borrow from the grandkids and say something along the lines of, ' oh you know how it was back then, I'll do me, and you do you.' big smile and subject change.