Volume (spatial). It takes up a ton of room inside the phone that could be battery.

I'm not particularly excited about it, but it's obvious why they'd want to do this, even if the phone doesn't get thinner, based on this picture from an iFixit teardown: https://d3nevzfk7ii3be.cloudfront.net/igi/fdaWRVGrZhxlZoJH.h...

And the interoperability. You don't need an "iphone" set of ear buds or headphones. So other than "aesthetics" by that meaning "different" I dont see much benefit and lots of usability downside.

I don't think so. If there were, studio-level gear wouldn't be using it (yes, they also use 1/4in jacks, but they are effectively equivalent in quality). It's highly unlikely that apple will produce something that produces better sound at that latency. I bet what they'll do is switch to a digital connector that also carries some meta-data about the audio.

For Apple it is probably just a space / size issue. It is probably one of the biggest things limiting them from making the phone thinner.

The socket tends to wear instead of the jack. This makes them more suseptable to damage. I wouldn't be surprised if a significant number of devices get warranty returned based on this.

It's too fat!