Yet, anyhow. If they ever lock you down to only approved headphones, then we've got a real problem, and not just for being able to do what you want with your music.
You can effectively make songs that only play on certain headphones or songs that play better quality when you have your beats plugged in.
This isn't the first time this has been brought up this was the first thing everyone had in mind when the rumors about Apple ditching the headphone jack first appeared.
With audio being pushed through lighting port in a digital format Apple knows for sure what device is connected to it, and even if you spoof the device id they can still use DRM because the device decodes the digital signal and if it doesn't have the correct set of keys or decoding configuration it would not be able to play the audio.
One way or another, the audio is cut off. Just because it's another jack/plug customers won't be upset?
Second is the subtler stuff -- like how the jack can now communicate about the music and the device with the phone, so you really could do things like have exclusive Apple music releases only playable on Beats, or (behind the scenes) have a higher quality version play on your Beats than your other headphones, reinforcing the illusion that the new port and devices are "better" than the old analog one (which is impossible). Or have advertising play on radio, except on headphones that have paid a premium to be "ad-free."
It also opens up much more positive possibilities, like the phone knowing the frequency profile of the headphones that are plugged in and automatically using the right equalizer settings to make it sound great. Or, simply wireless devices being able to charge through the port when plugged in. Or having headphones with memory that can keep a few hours of music on them 'synced' by plugging in so you don't even need your iPhone to listen.
So all in all, it's a set of tradeoffs, giving up some freedom and simplicity, for the opportunity of more possibilities in the future. It's difficult to say exactly how it will be used, but the realist point of view is that it's all ending up as the same analog sound in the end; there's only so much that can be revolutionized. Time will tell.
That said, this is only true as long as it's still a 3.5mm plug for the headphones. If headphones start directly integrating with the new port, this equation drastically changes.
If they ever...
Boiling frogs.