What Happened to Chat Bubbles / Heads in Android?

How the SYSTEM_ALERT_WINDOW permission has been abused over the years by malware creators?

Chat Bubbles aka Chat Heads is a user interface element initially introduced by Facebook Messenger back in December 2012. This feature allowed Android and iOS users to chat with multiple persons while using other apps at the same time. The simplicity was the foundation on which the popularity and likeliness of chat heads relied upon.