In many cases, visitors aren't using Google search because they want a webpage. They're using Google search because they want an answer to a question. Google is answering that question without them having to click through to another site, and visitors are fine with that.
Likewise, I wouldn't say that all of the online calculator websites are "losing" visits just because I plug 3^3 into my search bar and get 27.
Note that in some cases, Google has license agreements with the websites from which they gather that information, so while the visitor may never land on the source website, that source website still gets remuneration.
Besides, if you think it's bad that Google is providing content from other sites so that visitors never have to land on the source site, just wait until you hear about AMP ...