Eliminating the removable battery, IR blaster, and headphone jack freed up a lot of space inside the phones. And since space is a premium, they had to look at whether it was worth it to keep those features or not, ie were they wildly popular or was it only important to a small group of customers? Of those, I'd say the headphone jack was the only one that would meet that criteria. Unfortunately it probably took up the most space out if the three, which is why it got axed.
While I wasn't happy with companies ditching headphone jacks, I've since moved on, and not having wires in the way is nice. The only issue is having to worry about if the headphone's battery is charged or not.