The Sony Xperia ZR is water resistant to IP55 and 58, and that has a headphone jack.
I'm certainly not complaining about its omission on the iPhone 7 given that a dongle's included, but I doubt very much that waterproofing was behind its removal. More likely - they did it for marketing reasons in order to make the phone appear different and more sophisticated than its predecessor. Afterall, with the exception of the antenna bands and new 'blacks', the phone essentially looks the same, especially when a case will be fitted.
I'm certainly not complaining about its omission on the iPhone 7 given that a dongle's included, but I doubt very much that waterproofing was behind its removal. More likely - they did it for marketing reasons in order to make the phone appear different and more sophisticated than its predecessor. Afterall, with the exception of the antenna bands and new 'blacks', the phone essentially looks the same, especially when a case will be fitted.