Even besides the money they get from Google, Mozilla aims to support the web, much of which is ad supported. Blocking tracking by default says "we think website

Even besides the money they get from Google, Mozilla aims to support the web, much of which is ad supported. Blocking tracking by default says "we think websites can survive with context-based advertising without obnoxious tracking". Blocking ads by default says "we think the ad supported business model is not worth supporting". That's a much bigger step.