Firstly, there are several improvements:
http://chrome.blogspot.com/2011/09/new-stable-release-of-chr...
Secondly, Firefox's new release is the same as Chrome's. Every six weeks, like clockwork. More releases, less big features in each release.
The Chrome release cycle is meant to make sure not only features, but critical updates make it out to users on a timely basis. Every release isn't guaranteed to be feature-packed because that isn't the goal.
Ultimately it's about keeping the project on a steady rhythm of development which sees features and fixes out the door as soon as they're ready.
Don't assume things!