Big issue is Apple has no new innovative products. Apple Watch isn't really enough of new product to drive iphone like sales at least not yet and there is nothing else on the horizon.
Everything new maybe, but old audio gear, monitors/tvs/keyboards/drives, et c stick around a hell of a long time. I'll be surprised if my family's at more than 20% of peripherals, displays, and audio equipment on bluetooth/USBC in 5 years, personally. Probably more like 5-10%. 10 years? That's another story. Assuming the standard hasn't shifted again.
That's not much of an issue to the kind of customers that can afford a new expensive Apple laptop.
You mention: "monitors/tvs/keyboards/drives". Well, keyboards and drives are trivial, as they use USB. So those people can just buy a USB-A to USB-C cable for $10 and be done with it (no dongle required if the keyboard doesn't have a fixed cable, and hard disks don't have fixed cables in the first place).
As for tvs and monitors, not sure how hey wont be able to use them with the new Apple devices, but they can afford a new one if they are so inconvenienced to use an adaptor.
It's more that I can carry my 2014 macbook anywhere in my house or office or anyone else's and probably connect it to anything I want or need to, without an adapter. Works, say, 99% of the time. With the 2016 it would work 0% of the time today (well, audio equipment excepted I guess, since they weren't courageous enough to remove the headphone jack on the MBP, fortunately), and it would take a half-dozen dongles to come even close to that 99%. I don't expect the success percentage for a dongle-less 2016 MBP to go up much in the next 2 years. That makes stretching my 2014 for another year or two, or switching to another vendor, way more appealing than it might be otherwise, especially with the non-trivial price hike adding insult to injury.
[EDIT] OK, half-dozen was a slight overstatement. At least 4, maybe 5.
High end keyboards sometimes feature one. E.g:
http://www.coolermaster.com/peripheral/keyboards/novatouchtk...
That's what the forward march of progressing standards is about - you upgrade some, with adapters for legacy interfaces.