Could be a number of reasons. Two off the top of my head:

1. Avoiding content that could raise copyright questions (see the Copilot drama) 2. Eliminating original content also eliminates the potential for offensive/illegal original content (see China's attempts at censoring Hong Kong protests in video games a while back by simply having developers remove entire features supporting player expression (e.g. chat, signage, etc)).

So they can upsell that feature in a more expensive premium offering. They spent billions on this AI, they want to monetize it so they can't just give everything away for free.