The idea that the elimination of the 3.5mm jack has anything to do with waterproofing is a complete misdirection, as evidenced by the list of waterproof Android phones with USB-C and 3.5mm jacks.

Also, any modern phone with bluetooth is just as capable off running airpods or any other wireless headphones whether or not it also has a 3.5mm jack.

Lastly, eliminating the 3.5mm jack has nothing to do with making the phone thinner either. My jackless iPhone 7 is actually a few mil thicker than my older yet nearly identical iPhone 6 which has a 3.5mm jack.