I have an unfounded theory for why they added this Restricted Mode. My guess is that they're getting pressure from "Mom Activist" groups and credit card companies wanting them to remove all "explicit" content the same way that Itch and Steam has been lately. My theory is that this feature was created just so Google can point to it and say "see, we're going to great lengths to hide unsavory content from the youths, just like you want!". They're throwing a wide net to catch anything that could be remotely controversial, while making it actually rather easy for users to disable (I think it's two clicks from any page on the entire site?). They haven't publicly said anything about it, because that would undermine the whole reason they created it. Don't get me wrong, I'm not saying I approve of such a feature, but this is my suspicions of why they've added it and why it seems like such a purposeless thing, it's not actually something for themselves or their users at all.