We had been using this service to shorten our big and long webpages link from 2009. The service was closed for new users from May 2018 but now its officially closed for all users. The reason behind it is that their use had been so scarce and this tool was made for Google Toolbar and Feedburner.
Well, its nothing new as Google keeps on launching experimenting products or many new consumer products and also at the same time shutting down for eg. Google+, Hangouts when the response is less or if these projects consume more of Google’s resources without giving a good output volume.