It seems that a lot of them are sort of "off" by default to keep search focused on search. If you want to get an LLM summary of a search, for example, end the search with a question mark. Example: "what is gravity?" instead of "what is gravity".
I use that super often, probably in vast majority of searches. It's basically an llm synthesized version of the results. You can also get it by the shortcut `q` on the results page, or by ending your query with a `?`
The summarizer lives at a different page, here: https://kagi.com/summarizer/