With my 3.5mm jack comment, I guess I was being flippant. I know why they included it - because it's absolutely everywhere. On every piece of pro audio equipment, every professional camera, broadcast monitors, VTR machines, in every TV studio, recording studio, radio studio, every domestic TV/radio, every walkie-talkie, it's in cars, aeroplanes, trains, it's on games consoles... it's everywhere!
Any computer that is worth anything needs the 3.5mm jack.
But by removing it from the phone, all the people that use headphones in all the above situations then need to swap to different headphones or fiddle about for the adaptor (assuming they haven't lost it).
I guess my point was that including it on the MBP is Apple admitting that the analogue jack is far from obsolete.