Also, being realistic, I do not believe that many normal people try to summarize the full text of old public domain ebooks. If you search for Moby Dick, much better resources come up, and that is what you want a summary for. People want a summary when they are searching to know if they should read more.
Summarizing long articles, videos, etc. is why these summarizers are so useful, you talk about web search but what OP linked is not a search engine (the Kagi search engine is, but this demo is not, it is just a summarizer that you use if you already have, for example, an article found on HN), you are talking about two different tools.
