I recently doubled the thickness of my iPhone SE by adding an external battery. Fits in my jeans pocket fine along with several other things in the same pocket. If they can get it that thin, why don't they just add more battery and take us back to the time when we could run phones for weeks between charges.

[edit] I'll answer my own question. Nobody is going to replace an iPhone because it drops from 21 days battery to 14 days battery, but they probably will replace an iPhone that drops from 21 hours battery to 14 hours.