E.g. on Google if you search for "how to tie a tie", a little info box may pop up with step by step instructions. This content is taken from some website, but that website gets no page hits or ad revenue. Instead, Google gets to serve ads on the search engine results page.
(I don't know if this happens for this specific example, but Google does this for some searches)
Part of why sites participate in the infobox program is that in practice you do get quite a lot of hits from it: many people click through to see the answer in context.
(I don't know if this happens for this specific example, but Google does this for some searches)