It's not just content/info/data, it's a performance (in the creative sense).
Brands spend a lot of time honing their appearance - not just fonts and colours but the whole composition and visual pacing - their entire "say something without saying anything at all" aspect etc. Just walk through any place with physical shops and really look at how the stores have worked on their appearance and how they present themselves to customers. They're not just selling a product, they're selling a lifestyle/feeling/etc/etc. They're not just going to give that creative control away to some LLM.
Another way to think of it is instead of people watching a movie or play when they go to the cinema or theater, they're just given the script to read. Same information but the entire artistry of both the performers and the directors is totally absent, leaving it up to each reader to imagine the delivery of lines or the scene's setting etc.
I think on HN and in tech in general people seem to forget that "the first bite is with the eye", and that is why "normal people" never liked or used RSS. The desire to leave our mark and to create (and view!) visually appealing things seems to be pretty innate in humans - we've been doing it since cave paintings. I struggle to think of a world where we just hand that over to AIs and humans have zero creative control.