Why is outer space black when almost all areas of the sky is covered by stars? Like the Hubble Space Telescope has proven us, everywhere in the sky there is stars
user
Surprisingly, through observations made on the New Horizons mission, outer space is not black and might be brighter than we think. (Lauer 2021, "New Horizons Observations of the Cosmic Optical Background", The Astrophysics Journal)

Researchers went through images taken by the spacecraft's simple telescope and camera and looked for ones that were incredibly boring, the so-called "blank space" images, and subtracted all known source of light, including lights from stars, scatter light from the Milky way, and even light from hypothesized galaxies, and they are still left with plenty of unexplained light almost equivalent to the number of known lights.
assistant
Why is this light not visible when looking up at the sky?
user
Because this background light in space is very, very dim, and there are too many factors, such as bright celestial bodies, atmospheric light scattering, and artificial light sources used by humans, that would negatively affect our ability to observe it from Earth.

As such, this light can only be observed through a very powerful extraterrestrial telescope, such as the one used on the New Horizons mission as above.
assistant