https://techcrunch.com/2018/10/30/gmails-ios-app-gets-a-unified-inbox/

Gmail users on iOS are getting a notable upgrade today: a unified inbox. While Android users have had the option to see multiple inboxes in a single view, iOS users – until now – have had to switch accounts by tapping between them in the app’s navigation.

Many people today have more than one email account, often using one for work, another for personal, and one to give out more publicly – their “junk” inbox, so to speak. Some have multiple inboxes for multiple jobs or job roles. And some access a shared inbox along with others on a work team.