It's about how the brain works.
Camouflage works by breaking up the shape of the object.
Similarly we recognise shapes and motion.
The gliding and free flying scene have lots of young and not so young innovative instrument designers. Whilst I have had digital and strip displays the easiest and quickest to interpret are pictorial where a glance is enough rather than reading what the digits (strips) actually say.
Examples are the old wind arrow or a semicircular vario dial (with a trend arrow).
Whilst all work efficiently when one is in a high work load (stress) situation surrounded by twenty other pilots in close proximity, in turbulence and next to a mountain face the "modern" instrument presentation is virtually useless as my ageing brain doesn't have enough capacity.
And this isn't after 10 hours in a rarefied atmosphere in the middle of my biological night.