Yeah, I agree with the sentiment of your comment, but your facts are wrong because you haven't really internalized the fact that lawyers are a medieval guild. The reason you see "this is not legal advice" on posts by lawyers is that lawyers can get in trouble for giving legal advice in a HN post--they could be sued for bad advice, and someone could also very easily file a complaint with their state bar, and the state bar will take it seriously and could revoke the laywer's license unless they have been very, very clear that they were not giving legal advice.[1]

Is this really done to protect the public (as opposed to because state bars want to try to protect lawyers as the only people qualified to talk about the law)? I have my doubts, but I'd like to stay employed.

[1] Look at this example I found in 20 seconds of googling to see how talking about legal issues in a public forum can lead to a headache for lawyers: https://www.nvbar.org/wp-content/uploads/opinion_32.pdf. It looks like sanity ultimately prevailed (you don't form an attorney-client relationship by calling into a radio station), but I'm sure whichever lawyer did this spent years dealing with potentially having their career ended while this moved through the California State Bar's system.