For those who are wondering why, it is because over time Google has slowly integrated features of Songza into Google Play Music. What this means is that essentially both platforms are similar in nature which also means that the need for both of them to exist side-by-side is no longer necessary, hence the closure of the service.
According to the email, “It’s now time for us to focus on building a single, cohesive product. So as of January 31, 2016, Songza will become Google Play Music, and you will no longer be able to access Songza.com or the Songza mobile apps.” For active Songza users, fret not because the transition to Google Play Music (if you choose to use the service) will be seamless.
Songza writes, “Moving to Google Play Music is free, and your favorite playlists can come with you! Pinky swear. Soon, when you visit Songza, you’ll be greeted with a prompt that will let you bring all of your Songza listening history and favorite playlists over to Google Play Music — so please make sure to do that!”