My theory is that, just like with omitting a final comma in a list when not essential for meaning, publishers are trying to save paper and ink or pixels on-screen.
When I give a speech at a corporate event, I often ask those in attendance, ‘Do you know how to tell if you’re doing the job?’ As heads start whispering back and forth, I provide these clue: ‘If you’re up at 3 A.M.
