"Why does it matter if that connection happens via 8.8.8.8 or some other IP resolved by a different DNS server?"

By controlling the DNS server, user can early point doubleclick.net, google analytic to 0.0.0.0. That might be why google wants to control that in the Chromecast.

It is a continue war between Jedi the Hackers and the Empire. The young Anakin Skywalker - Do no evil Googlers have felt the (share holders) power of Dark Side. The power felt stronger as the G stock price kept going up.

BTW, one can also config a raspberry pi / openwrt device to have subdomain ip of 8.8.8.8 and still resolve the doubleclick.net or all other tracking websites to 0.0.0.0.

May the source be with you.