I think it is more a case of the advertisers, since there would be little opportunity to show ads.
Receiving traffic to sites is nice, especially for already highly-ranked results, but these are not the people buying the ads.
They could just as easily show ads in answers, the advertisers wouldn’t care. In fact, I can see how a major advertiser would rather prefer that an ad is shown in Google’s own trusted UI rather than on some random website next to who knows what sort of content (that motivation is behind YouTube’s “demonetization”).
OpenAI subverted this by riding on the “open” part of their name at first—before doing a 180-degree turn and selling out to Microsoft.