Firefox 41 will use less memory when running AdBlock Plus 11 years ago
They are.
Source: My employer (a major site with Alexa rank <100) contacted ABP asking to have our text-only, clearly-delimited sponsored search results whitelisted. They told us that it wouldn't happen unless we signed an NDA, paid them a share of the revenue difference, and installed a third-party script on our site to allow them to track our users. (We just laughed at them and changed our markup to work around the block.)