Re: Is anybody listening?
For people wanting to continually use a phone throughout the day, a Moto Mod battery pack is a better option than a removable battery since it incurs no down time whilst the phone is power cycled. For people wanting to extend the life of their handset by changing the battery, the cost of having it done by the original vendor or 3rd party shop is small compared to the original price of a premium handset (removable batteries are still found in low and mid range phones).
For safety reasons a removable battery must have a durable, hard to pierce shell (especially if it's slung in a kit bag) that is bulky (a slimmer metal shell would interfere with the phone's radios), so it results in several millimeters extra thickness over an internal-only battery that could otherwise be used for storing power.
The need for a removable battery is further mitigated by rapid charging and the ubiquity of power sources, planes trains and automobiles. In the case of no mains or vehicle power outlets, power banks are inexpensive and universal (an investment not lost when a phone is eventually changed) and, whilst ungainly, don't need to be attached to a phone for very long (rapid charging again).
Then of course there is the economics - why would a phone vendor go out of their way to appeal to a group who by their own admission only want to buy a phone every three years?
You could get yourself an LG V20 with a Snapdragon 820 SoC with removable battery - and as a bonus it not only has a 3.5mm socket but a socket driven by an ESS Sabre DAC and amplifier.
I'm not against removable batteries, I'm just trying to outline how the current state of affairs came to be.