Don't be silly. Who in their right mind would splash out funny money for a standalone dap for music when they could get a perfectly great smartphone which does so much more. You won't even know if someone calls you while you are listening to your standalone thing. This seems ridiculous to me.
These snake oil £1k+ DAPs that are springing up like mushrooms at the moment are conning the hell out of the poor gullible like nobodies business.
Good question...
How I see it, and you can track my history of phones if you like, had too many to list whilst replying to this on my phone, is that having a higher end DAP, the sound quality is more of an important to the designer, and you can hear that so so easily...
It is the difference between, and find your own analogy as you wish, having cigars instead of cigarettes, a fine wine instead of cider, a 4k TV instead of a crt, much more of a window into the music...
I have been one of the very strongest advocates of using a phone instead of a dap, and whilst at the X5 class of DAP I WOULD agree with you, stepping up to the next level, SQ does leave phones behind...
If you're that concerned that you'll miss a call, that is a life choice, me, I'd rather have great SQ, and feel my phone vibrate in my pocket...