How many lightning headphones do you have around the house?
Let someone else make the transition! I like the analog headphone because I've got plenty of them if I misplace them and do not like having the phone next to my head to talk. Be interesting to see how this works out for apple.
Apple will give you a free pair right out of the box. And you'll be able to buy an adapter for the other equipment you use. Problem solved.
Okay I don't really care about having to switch to lightning headphones for my iPhone, but I do care that I have to use headphones that won't work with whatever other device I'm trying to use. I frequently will take headphones I'm using with my iPhone, unplug them, and plug them into my Windows PC. Losing that will be annoying.
I'll have to keep track of "Oh these are my iPhone headphones, and these are my computer headphones. Oh and these are my old iPad headphones. If I take this pair I can use them with my iPad and maybe someone else's phone if they want to show me something, but I can't use them with my iPhone. I can use these with my iPhone but not with anybody else."
The beauty of this, is for new Apple products, you won't need an adapter. For legacy equipment, you'll simply have an adapter already plugged in to your PC that will take your Lightning headphones, so you don't need to keep track of multiple headphones, unless you just want to. And if you need to use a portable legacy product like an iPad 3, you'll buy an adapter. Just like I had to do after I got my iPhone 5S, in order to use the same charging cable with both -- not wanting to carry around 2 different charging cables.
Hopefully the adapter is just a cable that splits into two ports, a 3.5 mm headphone jack and another lightning cable. I don't want a rigid extension of the phone, rather an extended cable. That's just asking for a broken lightning port.
The best adapters won't be rigid, they will be simple flexible cords with a Lightning connector on one end, and a 3.5mm jack on the other. It will add a couple of inches of length to your headphone cables, and likely be mostly invisible to the user in the way it works. Some will have a pass-through Lightning port for charging and listening at the same time.
I'm all for removing the headphone jack but I don't think now is the right time. The Lightning port came with increased speed and a neato reversible plug. I can't think of any benefit from moving the headphone jack into the Lightning port, especially since headphones over Lightning are very rare and specialized. Also, with USB C gaining slow traction I don't want to have to get USB C to Lightning adapters...
The fact that Lightning audio products are proprietary and "rare" is exactly what this move will fix -- developers have no interest in serving a market which has the option of a cheaper connection. Take that away, and developers have a captive audience for which to serve their products. Ultimately this is a step in the right direction for the consumer. And there's no time like the present. Apple just released an ultra-thin MacBook with room for only one port -- the reality of which is has two, but the only thing the second port can do is supply analogue audio. If Apple switches to Lightning on their flagship product, that paves the way toward removing the 3.5mm jack from the rMB, and replacing it with a far more versatile Lightning port, that is also a just as capable backup to the single USB-C port. For Legacy Macs, they will need adapters for the new technology, just like every Mac and connector change before it. And ultimately, while you can't think of any benefit, there are. If nothing else, the move from the bulky 30-pin connector was more about saving space inside the phone, than the move to digital tech. One could say that was a bad time as well, but the longer Apple waited, the more 30-pin dock connectors would be on the market and the more licensing they would have to issue since they couldn't divulge their plans, creating more frustration with the developers when the day did come. It's inevitable that in order to make mobile devices smaller the 3.5mm jack will have to go, especially as the main stream moves toward wireless devices as they get better, and more convenient, with longer battery life, etc. And it helps Apple squeeze more value into their phones without making them bigger, or making other compromises.
So the question isn't why now, but why not now?
music. 
