Because this is for stupid people, it will be done in a stupid way. They aren't interested in cash bought anonymous auth tokens that require you to be over 18 to the store clerk or whatever. In part this is stupidity, in part this panic is also about "pedophilia" so they want to make sure whoever is talking to their daughter who is using a parent authenticated tiktok account gets arrested promptly because he showed his passport as opposed to being there with an untraceable anonymous auth token he bought for $1.99 at a random convenience store.