Google Chrome already ships with an ad blocker (it is in the "site settings"). It is, however, very weak.
I think Google would love to block ads more aggressively, but the conflict of interest is so obvious it is going to be raining lawsuits the instant they do that.
It really makes me wonder what the internet would be like if google had built microtransactions into a browser to support their sites instead, or as a complement to ads (e.g. an advertiser can pay for your time on the site in exchange for an ad, and google would only middleman the ad negotiation, not the transaction).
I think the surreptitious tracking is the real problem. I don't mind ads on podcasts, because their tracking is explicit and opt-in ("enter our show's promo code on the sponsor's product page.")
Likewise Google Contributor did not reduce tracking, which is why I never signed up.
I think Google would love to block ads more aggressively, but the conflict of interest is so obvious it is going to be raining lawsuits the instant they do that.