I think youtube serves ads from its own domain, as a first party. This makes it harder for a pihole to block. Ublock does it differently, looking at elements et

I think youtube serves ads from its own domain, as a first party. This makes it harder for a pihole to block. Ublock does it differently, looking at elements etc...a pihole just tries to block dns requests to ad domains, not looking at code that your browser is trying to load.