Google is an advertising company first and foremost, lest we forget. They want to create ads people want to see, they say, but I find it hard to trust their motives. It comes as little surprise they want to clamp down on browser extension based adblockers as Ars recently covered.
Fortunately, there are other ways to block ads which are more effective anyway. Every OS has a hosts file, which is simply a plain text file that can route internet traffic from one host to another. In Linux and Mac OS X the hosts file is in /etc/hosts and in Windows it is in C:\Windows\System32\Drivers\etc\hosts and editing it will require sudo or Administrator rights.
Once you have your hosts file open, we are going to add a bunch of entries to it that will take traffic from many thousand known ad-serving domains and route it to 0.0.0.0 which is equivalent to a digital trash can. There are options for host file ad blocking. Personally, I use the list from mvps.org but the list from Steven Black looks even more comprehensive, and it is segregated out into the types of traffic you would like to block: unified hosts for ads, fake news, gambling, porn and social. Both of these lists are completely free of charge. What you want to do is get your list loaded into your browser, then select all and copy it to the clipboard. Next, simply paste the text into your hosts file. You may want to take a backup of the hosts file first, especially if you have existing entries that you will need to add back in. Once this is done, ad blocking will immediately take effect, no reboot or logout required.
Supposed you are on a device which does not allow access to the hosts file, like your phone or tablet. Sure, there are plenty of ad blocking apps which you could use, but I have found a better way. On your device you can change the DNS settings for WiFi connections. A simple google search will show you how to do this on iOS or Android. Armed with the knowledge of how to change this setting, you will need a primary and a secondary DNS server. There are several free DNS servers to use AdGuard is quite reliable and Alternate DNS has not failed me yet. In my setup, I use my primary server from one and secondary from another, just to keep them honest although this is not necessary.
In changing the DNS, we are still trusting someone else with our internet traffic and DNS hijacking is a real threat. How do we know our DNS server settings aren't being compromised? I use a router checker from F-Secure to verify the DNS settings. This tool is also free, and entirely online. It will give you an expanded view of your DNS settings if you wish, and its standard output is a simple Green/OK Red/NotOK. So there you have it, a completely free way to block ads, without relying on the browsers to not undercut their own business model!
What about when you're on the cellular networks from you phone or tablet, you ask? I have that figured out as well, but I'll save that for another day...