Google's android products are still going to phone storage
Many apps require to be stored in internal storage. This is by design and it cannot be changed. Most of the Google apps such as Hangouts and GMail cannot be stored to external storage (i.e. SD Card). So whenever you download an app that requires internal storage it will be stored in internal storage regardless of your app storage setting.

P.S. Developers prefer internal storage as external storage is generally slow to read and affects the performance negatively.