We are the developers and we love to work at night time. At night the human brain functions more than during the day times.
Computer programs are designed to work best during day times. Most programs have bright UI so it's clearly visible during day times. Mostly it's because all the computer-related jobs are done in day shifts. And that is well thought out.
Nowadays most developers also work in night shift. The night is dark contradictory to the bright UI of the operating system or the application. It's not comforting to look at a very bright UI and work simultaneously.
Recently developers are releasing updates to support dark for various applications. All major operating systems are supporting dark mode.
Dark mode converts all bright elements of the application or OS to a near-to-black color. All texts are converted to a white-like color with high contrast to black. It will help the developer to see text easily at night time.
The dark mode also helps save energy for portable devices like mobile and laptops. When OS/application shows black color on any display panel it consumes less power compared to bright colors like white. It dramatically reduces power consumption.
Recently it's a trend to have a dark mode. Without dark mode application is incomplete. Many developers consider dark mode as PRO mode. As most developers love to work till late at night and dark mode really helps them to continue work longer.