If you don't like third party cookies then I encourage you to go to chrome://flags/ and Enable the 'Block all third-party cookies' experimental feature.
Defaults matter. An extensive body of social science research tells us that users stick with the default settings.
In the area of security, Google recognizes the importance of setting safe defaults. See: "99.99% of Chrome users would never change the default settings. (The percentage is not an exaggeration.)"
Simple as that.