I worked on the iPhone at Apple and sat in many meetings where the product design and electrical engineering leads would almost come to shouting matches over fr

I worked on the iPhone at Apple and sat in many meetings where the product design and electrical engineering leads would almost come to shouting matches over fractions of millimeters. The engineering was fascinating. Everything inside the phone wants to be away from everything else. For example, the radios have power amplifier chips that are hot spots and need to be kept away from the battery to avoid exceeding its thermal limits. The antennas need to be kept away from noisy chips that would affect their reception. There are external connectors and SIMs invading the case. Once that is all crammed in, they need to drop test the whole thing and hope it doesn't bend or shatter. It's really challenging to cram that much stuff into a constrained enclosure, and all of the layers add up. As I understand, a removable battery takes up a lot of area, because you need clearance below it and space for the mechanical fasteners. It also breaks up the pristine surfaces that are a big part of Apple's design language. The individual industrial design, product design, electrical, and RF design/antenna engineers responsible for each part aren't thinking about sales in two years. They want to make their piece as good as they can and hit the schedule.