Dark app themes and white on black UI are prevalent in games and game development tools for a reason: Games are often enjoyed in the dark to heighten immersion.
There’s lots of good reasons for apps having dark themes, especially when you work later at night and a bright white window appearing where grays were before can be jarring.
Generally, white text works best against a dark gray background rather than a solid black one, which causes glare. Bolding text makes it much more readable on a dark background.
Unity Editor’s dark theme requires a paid version to use it.
How to get dark themes in development tools
Asana Dark Cobalt
Office Gray & Black
Office has a dark gray theme. They released test builds with a black theme that was disabled in later versions but still exists and can be enabled via a registry edit. Hit Start, type Regedit, navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\UI Theme and set UI Theme value to 4.
Windows 10 Anniversary has a dark theme option, earlier versions can be enabled via WinAeroTweaker.