Often because (as in this case as well) they are not regular LCD or calculator-like segmented displays, but rather Vacuum Florissant Displays. VERY satisfying hue they emit.
Old gas-plasma displays are awesome there’s something so retrofuturistic about them, they’re a cross-breed between CRTs and LCDs.
Some laptops specially those for mil applications came equipped with them they also were (and there are some still running) common on industrial machines due to their ruggedness.
https://en.wikipedia.org/wiki/Vacuum_fluorescent_display