There are few possible reasons for this.. a) This would require most other web analytics providers to make changes to heir code and adapt to this nw referral pattern which would need some time. Webmasters would definitely need an alternative option to get stats during this latency period and might adopt GA. So its virtually creating an opportunity in the analytics market to promote GA further.
b)From the URL string it seems that now Google would be passing each click through its server therefore getting a more accurate data about the CTR for each site on specific keywords. This data might be useful for them to improve algo and enhance relevance in their organic results
c) They are passing much more information through the referrer string now. Though they have not clearly explained all the parameters in the new referrer string, I doubt that now they will also tell you the exact ranking for the website on a particular keyword through the params in the URL.