The chatbot user benefits from having one great answer pulled from the best sources (and no ads), but the websites that underpin the chatbot’s usefulness will no longer have monetizable traffic. In the long-term this disincentivizes people from publishing online, which would reduce the quality of not only the chatbot output but the web as a whole.
Imagine local news being totally unavailable online by any means because the rise of chatbots means that nobody can make any money writing about local news.
Edit: A first reaction to this might be “have the chatbot show ads and share revenue with its sources.” This probably wouldn’t solve the problem. Journalism (and many kinds of writing) would be a less attractive career if your readership consists mostly of people getting second-hand summaries via chatbot. If chatbots do become popular, I worry about a bleak future where journalism and other writing is replaced by an anonymous blob of underpaid foreign laborers whose only job is to shovel up-to-date facts into chatbot databases.