AI needs to be kept up to date with training data. But that same training data is now poisoned with AI hallucination. Labelling AI generated media helps reduce the amount of AI poison in the training set, and keeps the AI more useful.
It also simply undermines the quality of search, both for human users and for AI tool use.
SEO is a slippery slope on both sides because a little bit is good for everyone. Google wanted pages it could easily extract meaning from, publishers wanted traffic, and users wanted relevant search results. Now there's a prisoners dilemma where once someone starts abusing SEO, it's a race to the bottom.
I reject this emphatically. Google should never have been in the business of shaping internet content. Perhaps they should have even gone out of their way to avoid doing so. Without Google (or a better-performing competitor) acquiescing to the game, there is no SEO market.