Because it sucks! It's badly written, too long, and often pointless. I don't like reading tacky, useless garbage
If people used AI to get the scaffolding of their article going and then re-humanized the entire article, it might be really good, still at a fraction of the time it would have taken to write it themselves, but no one seems to want to expend enough effort to go the extra mile.
With video it's pretty well hopeless, unless the AI helps accelerate fully human traditional production techniques.
With music, there might be a middle ground, I have had some success getting AI to generate good sounding loops to use in electronic music production, but it was just a matter of brute forcing enough outputs to finally get something decent, which isn't fun at all.