On reflection, most adults didn't care much about underage sex until they were able to leveraged it into public outrage - and therefore power for themselves.
The proof of this lies with pre-1980s generations of child sex abuse victims, who knew (or quickly learned) to not go to adults in authority - especially police. At best, they could be expect to be ignored, marginalized and/or gaslighted. At worst could be more abuse, even if 'only' verbal, physical, etc.
Reality is that most adults in authority didn't give a crap about child abuse until they could use abuse allegations as a weapon.
Once they (police, legislators, administrators, etc) gained that power, all kinds of things suddenly became abuse, including consensual sexual activity.
"Think of the children" tends to be code for "figure out how to leverage the children".