It's not scraping static text in order to point you to those sites, it's using the features of the site to perform a service better than you can do yourself. It's completely different.
If I made a site that claimed to help you with your math homework and simply sent the queries to WolframAlpha, that would also not just be "scraping."
Google has donated many millions to the Wikimedia Foundation, basically in payment for this.
(But, again, there's a difference between scraping and echoing a request on another site and waiting for its response. The latter is basically unauthorized use of its API, not scraping.)
If I made a site that claimed to help you with your math homework and simply sent the queries to WolframAlpha, that would also not just be "scraping."