Was NOTHING gained from removing the Floppy Disc drive? Was NOTHING gained from removing the Mac's serial port? Was NOTHING gained by removing the DVD-R drive? Was NOTHING gained by removing FireWire ports? NOTHING?
Removing legacy ports forces the technological march forward. That's how standards are adopted. Of course, Macs could have accumulated all of these ports and drives over the years since there would have been people who have wanted to use them, but then new more advanced ports and formats would have never been widely adopted.
We'll see in a week, but I'm convinced that Apple will be pushing for wireless headphones. Future wearable products will rely on not having cables of any kind. Right now, that's the Apple Watch but in some distant future, Apple glasses might join in. In the more immediate future, having wireless AirPods in your ears with Always On Siri connected to all of your devices (not just one) is a major advancement from the standard we have today.
Yes, bluetooth headphones have been around forever, but when they become a priority, technology will push forward and it'll become the standard. Then, we'll look back and wonder why we ever put up with dangling cables from our ears.
People that can't see any benefits, won't ever see any benefits. They'll just be dragged along kicking and screaming the same way people that loved all those ports you mentioned were. Then later on they'll be one of the first to say Apple was right getting ride of the port just like in the past too.