This.
In my extended family, there was a case where several siblings were sexually molested by a very close friend of their family. The kids had been taught that if a Grownup said “you must do X,” then they MUST do X, or they were disobedient and would be spanked. Period. “Never ask why” was literally a rule in their house. And since Uncle Steve (name changed) was practically family, they HAD to hug/kiss him. And if he wanted to touch them, he got to, because he was an adult and he said so. It didn’t matter that they didn’t want him to touch them–they Had To Be Polite. Throw in a strong family culture of “any mention of your private areas or anything remotely relating to sex is immodest, sinful and shameful,” and…well, while even their parents would have said that of course sexual abuse of a child was wrong, when Uncle Steve started taking them into his bedroom and doing other kinds of touching that they weren’t okay with, how were they supposed to go to their parents and say, “These things are happening and I’m not okay with them” when it had been made clear from day one that a) the kid didn’t have a right to not be okay with being touched by Uncle Steve, and b) so much as saying “bottom” would get them in trouble anyway because mentioning such things is immodest and disgusting, and in any case, they shouldn’t know anything about That Kind of Thing?
Learning to follow social norms is, indeed, important, but they don’t always have to involve close physical touch. I would never require a child to hug someone, while I would require a child, given sufficient intellectual development, to say, “How do you do?”, shake hands, and so on.