Why would people switch to a browser in brave that tries to sell you some crypto currency and has its own ad network? Even if you want to use a chromium based browser because of issues with Firefox, there's much better available out there.
They haven't been trying to sell me anything and setting up their own ad system independent from Google is a good thing, esp. when it's transparent and optional. Brave has its problems but force-feeding users with ads or crypto isn't one of them.