Great question. When the "Semantic Web" hype train rolled through back in the day, I asked the same question. I got a lot of hand-wavey answers about search engine understanding semantics of markup. Also if you use <b> instead of <strong> you are a barbarian.
In theory, more information would be easier for a language model to extract meaning from though.
In theory, more information would be easier for a language model to extract meaning from though.