For starters -- it's too late not to buy an iPhone 7 or return it for someone who bought it because they were promised AirPods by the end of October -- about a month after the phone went on sale. In fact, I'd love to see someone return it for that reason just to see what Apple would do.
Second -- BT is not popular with many people for several major reasons:
1) it's difficult to use, mostly revolving around pairing issues
2) it suffers from reliability issues like dropouts and lag
3) they tend to be bulky, with cables linking earbuds, etc.
4) battery life tends to be limited, and unpredictable, especially on more portable models
5) they tend to be expensive
6) there tends to be a lot of low quality offerings in the low-end of the price spectrum that have turned people off
7) they offer lower quality audio than wired alternatives
In removing the headphone jack, Apple needed to offer an alternative to ameliorate the removal of the headphone jack, about which Apple was on the defensive from the moment they took the stage, and offered little legitimate support for doing. Yes Apple offered an adapter to continue using the old 3.5mm headphones -- while that mitigates the decision somewhat, it was more akin to pouring salt into the wound. Then they bundle Lightning EarPods with it, which could have been a huge positive, but the fact they can't be used with anything else -- in particular a Mac -- makes them less than an optimal replacement for the headphone jack.
So Apple made their agenda clear -- wireless is the future. Not only that, but they tell us they understand that BT is a "bag of hurt" to use a phrase Steve Jobs once applied to another popular problematic technology for Apple. In response they give us AirPods which solves 6 out of the 7 issues most people have with BT:
1) Ridiculously simplified pairing between Apple devices
2) No more dropouts or lag
3) ultra slim and compact design
4) Apple offers the longest battery life available for such a tiny device, with quick charge boosts offering 3 hours for every 15 minutes, up to 24 more hours. It also offers single pod use thus extending mono listening up to 53 more hours, without interruption.
5) For the technology offered they are somewhat reasonably priced.
6) Apple is a trusted name in quality, and has produced a product specifically designed to work with the iPhone 7
So Apple had to release this product with the removal of the headphone jack to demonstrate that wireless was indeed the future, since the existing BT market is generally not good enough to satisfy the many potential customers who have tried BT and had a bad experience and rejected it, or are confused by the offerings and limitations, or frustrated by the limitations of power, reliability, and complications of pairing. Not to mention their paucity of support for Lightning options. The AirPods are a huge step forward. The Beats offerings are likewise important -- though the only two currently available come with the added inconvenience of using micro-USB connections rather than Lightning, not to mention added bulk and expense over standard earbuds. And since Apple couldn't really address the audio quality issues and cost at this juncture, they offered an alternative via the inexpensive adapter, or Lightning (albeit limited).
