This is a new line of business that provides them with more ad space to sell.
If the overview becomes a trusted source of information, then all they need to do is inject ads in the overviews. They already sort of dye that. Imagine it as a sort of text based product placement.
You might think that's the correct way to do it, but there is likely much more to it than it seems.
If it wasn't tricky at all you'd bet they would've done it already to maximize revenue.
It never will. By disincentivizing publishers they're stripping away most of the motivation for the legitimate source content to exist.
AI search results are a sort of self-cannibalism. Eventually AI search engines will only have what they cached before the web became walled gardens (old data), and public gardens that have been heavily vandalized with AI slop (bad data).