This is because google docs is now widely used as a malware vector.
Send the user to a google docs page, and because it is on the google domain it is trusted by corporate firewalls and AV scanners.
The 'tracking' is in fact this page:
https://www.google.com/url?q=https://wikimediafoundation.org...
And that alerts the user to the fact they are leaving google and ending up on another site - which hopefully reduces the effectiveness of using google docs to distribute malware.
A feature request/complaint is that it doesn't support hovering to see the target URL/check if the particular tracking domain is supported, for example Tom's Hardware uses a "georiot.com" tracker that embeds GR_URL=https%3A%2F%2Fwww.amazon.com%2Fdp... %3Dtomshardware-us-1038331347314950500-20... and doesn't successfully parse out the raw amazon.com/dp/[product ID] link.