Why is a printed photo not as bright as it appears on my phone?

Colors of electronically displayed images differ from those of printed images because active and passive light sources have different operating principles. Electronic devices use RGB color space while printing devices use CMYK color space. These differ in both color range and conversion algorithm, resulting in slightly different color effects.
A printed image will appear closest to how it looks on an electronic device when the screen's backlight is set to the lowest level, and the brighter the screen backlight is, the greater the difference.