just why ? ...

[Aremis]

Actually, if you compare it to some of the endgame gear from before Heavensward, some of the Coil gear has better stats despite the lower ilvl when comparing the non HQ stuff. So I think you will still have people running coil and other endgame content. And, as someone else already pointed out, some people will run the old content to get the gear for glamouring over some of the new gear.