The controversial switch from the ellipsis in Windows Phone 8 to the hamburger menu in Windows 10 for phone was explained by a former, and anonymous, Microsoft employee during a verified Reddit AMA session this week



From Windows Central:

The employee stated he worked as a "design lead" on the new version of Office for Windows Phone but left Microsoft about a year ago. He also discussed and debated the reasons why Microsoft made the switch in a video, along with placing a navigation bar on top. Here is what he wrote during the AMA session

  Here is why Microsoft wants hamburger menus in Windows 10 for phone