Because the training in "deep diving into something" is evidence that the person can learn some other thing over the next few years. It is a tenuous connection

Because the training in "deep diving into something" is evidence that the person can learn some other thing over the next few years. It is a tenuous connection at best. It works somewhat in STEM because of the mentioned deep trees: some people are just naturally curious and will get to the bottom of anything, be it DS&A, circuits, complex analysis, or accountancy.