Well they are so vital the 757/767/777 don't even have them. Winglets are of questionable value to a shorthaul aeroplane where a high percentage of the flight is at lower speeds. They are optimised more for the high speed cruise. Even the 747 with its 6 foot winglets can quite happily fly without one. And the pilots wouldn't even begin to notice!
YOU show where your difference of opinion is valid considering BA is quite happy to send a 319 out on passenger service without one for an extended period!