Some think that search engines shouldn't index pages that include search results. Why clutter the results with pages that show another list of results when you could send users to the most relevant pages?
In some cases, search results pages are useful, but it's a good idea to know in advance that a page only includes search results. Google started to show a label like "Matches 1-50 of 100", "Results 1-24 of 56" or "33 results" next to the snippets. For example, an Amazon page that includes a list of Star Wars-related products shows this label.
Another example is a store that sells games: