Why does ad blocking always have to be relegated to an extension? Browsers build in so many things. Why do they all draw the line at a feature like ad blocking that every user wants?

Because modular architectures are good? I don't know what to say here. Even if it was built in it should be a built-in extension.

Because they want a level of plausible deniability.

The way uBO works already provides a layer of plausible deniability. It's just a content blocker that loads filter lists maintained by other people.

I'm not sure if you responded to the wrong comment, but the gpp was suggesting building it in by default.

If Firefox included it by default then it would remove a layer of deniability.

What do they need to deny? Ad blocking is clearly a feature many users want. It’s often the only extension people install. If I were Firefox, I’d build it right into the core of the engine. Turn it on with a checkbox and/or custom blocklist sources.

google money could dry up right quick. extension route gives them some deniability.

Yes, I meant building it in by default won't remove any deniability, because it will just be a content blocker where users can load their own filters (with maybe some adblocking filters suggested by default).