It does not prevent a bot from using your ID. But a) the repercussions for getting caught are much more tangible when you can't hide behind anonymity - you risk getting blanket banned from the internet and b) the scale is significantly reduced - how many people are willing to rent/sell their IDs, i.e., their right to access the internet?

Edit: ok I see the argument that the feedback mechanism could be difficult when all the website can report is "hey, you don't know me but this dude from request xyz you just authenticated fucked all my shit up". But at the end of the day, privacy preservation is an implementation detail I don't see governments guaranteeing.