It's not a family friendliness issue causing this, it's an 'advertiser friendliness' one.
Anytime an ad was shown on a slightly controversial video, an internet outrage mob would descend on the advertiser saying how dare they provide money to <odious cause>.
Advertisers pressured Youtube for ways to advertise only on non-controversial videos. Youtube responded by demonetizing anything even halfway controversial.
Take something like the Rubin Report [0], which is reasonably family friendly but that covers socially/politically controversial topics and/or speakers.
Not too long ago, a large amount of their back catalog was demonetized. It's not 'advertiser friendly' because sometimes even just the presence of a controversial speaker is enough to bring a hate mob down on anyone advertising on a video with them in it.
While you don't have any inherent right to, in practice you can post a pretty wide range of content to YouTube without charge. But certainly no one has an obligation to pay you for that just like no one has an obligation to pay you for writing a blog on pretty much any topic you desire.
Anytime an ad was shown on a slightly controversial video, an internet outrage mob would descend on the advertiser saying how dare they provide money to <odious cause>.
Advertisers pressured Youtube for ways to advertise only on non-controversial videos. Youtube responded by demonetizing anything even halfway controversial.