I haven't done much research on this topic yet. But it's my understanding that, to sum up:

1. It's easier not to target children.

2. This is more of a nuisance for established channels, as they have to edit every video and mark whether it's directed to children or not.

That's if I'm not wrong. I mean, I've mainly gotten my information from this one video so far: https://www.youtube.com/watch?v=3GwDrHOe43E

I'm only a new creator so it's not really going to be much for me to worry about, and I can't think of a single reason why anyone under the age of 13 would want to watch my content anyway. It's about as boring adult topic stuff (building a business and corporate life rantings) as you can get.