Surfin' Safari - Blog Archive » Introduction to WebKit Content Blockers
www.webkit.org/blog/3476/content-blockers-first-look
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
We have been building these features with a focus on providing better control over privacy. We wanted to enable better privacy filters, and that is what has been driving the feature set that exists today.