yeah I thought about that too (and here comes another wild guess lol).
I feel like the intention is not to say you need to be 18 years or older to use the site (I have a feeling a big percentage of the users aren’t, and personally don’t see why they would need to be). But the claim of “not directed to children under 18” (to me) in actual terms seems more like " There’s no age restrictions to use the site, but there is in terms of legal data collection" and I don’t want little Jimmy’s mother suing me for the automated data collection process.
I dunno, I’ll stop speculating now 
hopefully Justin can clarify more accurately for us, I too am not a fan of it, but I understand the potential implications of not doing it…I’d rather this then having to send Justin a selfie with my government ID and a piece of paper with my name and birth date written on it, like I had to do with the crypto exchange lmao.