Compare with organic food: is it true that non-organic food can be healthy? Sure! Then why do people prefer organic food? Because it's just not worth it for them to figure out which one is healthy/unhealthy.
Similarly, it's just not going to he worth the effort to figure out if some AI-generated content is genuine or trying to astroturf. If there will be a "certified human" badge, people will use that as a positive signal.