Linked from
The 12 pages that link to White point, each with the reason it gives.
Color spaceRelated: A reference white helps define how a color space interprets neutral colors.
ChromaticityRelated: Display calibration sets a white point as a target chromaticity.
Display P3Related: Display P3 uses D65 as its reference white.
Adobe RGB color spaceRelated: Adobe RGB uses D65 as the reference white for its encoded colors.
Planckian locusRelated: Locus positions help specify warm-to-cool white points.
RGB color spacesRelated: It establishes which RGB mixture is interpreted as neutral white.