The material and monetary cost of the number of wired headphones I've destroyed in the 6 years before I got wireless head phones (because there was no realistic way to stow the cabling for the activity I was involved in) probably approaches the cost of the 2 pairs of wireless headphones I've owned in the last 6 years.
I don't think they cut the headphone jack just to sell these headphones. While it is true that you can make a headphone jack as water-resistant as the rest of the phone, every hole you put in the phone adds to the design and assembly cost to maintain the same IP rating. And each hole significantly adds to the complexity of repairing that phone in such a way that it maintains that IP rating after the repair.