I've learned to be less outspoken as a form a self-defense. Your observation about how some kids are raised being told, "you're opinion doesn't matter" and/or "don't talk about yourself" is one reason. Apparently, my parents indulged me by asking me what I think. Then again, they also encouraged me to be open-minded and curious about other people's opinions. I've met people who get really pissed off when anyone (me) expresses an unsolicited opinion, and who can't express their own opinions without discomfort. They are taught that only those in authority (typically straight, white men) are allowed to express opinions. They are taught it's impolite to talk about yourself, and as I've gotten older I can see the virtue in that. Yet--unless we speak from our own experience, we can't change the current toxic power dynamic.