lols... I'm ancient... 12 is not a young age for engagement or marriage for humans, It was good enough for 1000s of years... I'm not personally interested... but I still remember when I was 12 being informed by my great grandmother that she had married her one and only husband at 12, 2 months after her birthday, she was his 3rd wife, the first died in childbirth, the second to disease, he was 31... the modern age of under 18 is to young, is really a modern convention. People's attitude towards it is rather a forced out rage added since it became law. A common effect in human history is that when a law is created, added, enforced, removed etc. the generation that is present is out raged about it, but in 20 years it becomes the "common sense" to the the next generation. Pre WWI it was common for women to be married off at 10 to 14, and men to be required to continue to work for their father up until their late teens.
In human history generally ages are pushed to older as a requirement for more time to be invested in training increases, so as education needs and population size increase, ages are pushed toward 18+, such events occurred during augustus ceaser, in spain in the 1200s, in greece 200 BC, etc and such events usually preceded a culling of the group (plagues, wars, etc.). As population size decrease and skills needed becomes more primal/survivalist in nature... we end up with ages being pushed toward puberty (10-14), such as it was in the americas from throughout the western expansion of the country up to the events that led to WWI.
So here's a thought experiment: how many generations do you think it would take before humans revert back to such a level again? Possible examples of such events that may evoke it: nuclear war, environmental collapse, in the negative and in the positive, new "colonies" say on the moon or mars? Personally I think that as the amount of skill needed becomes centralized into a specific set of "survive skills" such "places and events" will revert to lower and lower standards, not because they want to, but because they will need to, for survival.
So yes I can see that some may have an aversion to it... but I think its only an aversion, because they were given a law to make them be averse to it. kobolds are marrying at 5 and 6 years old... OMG!!!! blah.