> Perplexity also attempted this, got sued by Amazon and it appears semi-abandoned.

Any details on that? I feel the answer is more likely there than in "friction".

Hardly any purchase of consequence is so sensitive to friction that the difference between Google Search and an LLM response matters (especially that in reality, we're talking 20+ manual searches per one LLM response). I.e. I'm not going to use LLMs advise on some random 0-100$ purchase anyway, and losing #$ on a ##$ purchase due to suboptimal choice is not that big of a deal - but I absolutely am going to consult it (and have it compile tables and verify sources) on a $500+ purchase and for those I can afford spending few more minutes on research (or rather few hours less, compared of doing it the usual way).