Google Talk was replaced by Hangouts back in 2013. Before then it was one of the most used chatting client over PC. This isn't really that big a surprise since the end of Google Talk was long time coming.
Scrapping Google Talk was confirmed by Mayur Kamat, Product Manager for Google Voice and Hangouts, who announced on Google+ that starting 23 February this year, the Google Talk app for Windows will cease to exist. Accordingly, existing users will have to migrate over to Hangouts for the latest communication features. The company had been alerting users that the Google Talk app for Windows will stop working since February 16, 2014