My understanding is that the two things go hand-in-hand. The ad-blocking is for users, while the cryptocurrency is to remove the incentive that sites have to show ads in the first place. Without the cryptocurrency component, you’d just see sites implementing anti-Brave’s-adblock features in a never-ending arms race, like we have with regular browser-extension ad-blockers today. With it, sites affected by Brave’s ad-blocking have something else they can choose to implement (a crypto paywall just for Brave users) that will give them even higher ROI than anti-adblock features would. It’s an “economic approach” to privacy.