It's always intrigued me why top-of-the-range iPhone batteries do tend to be smaller than their equivalents in Samsung high-end Galaxies etc. Do other manufacturers manage to create more free volume inside their cases compared to Apple so there is more space for a bigger battery and if so then how? Is an iPhone PCB bigger due perhaps to the A-series SoCs being bigger than Snapdragon etc? Do other manufacturers use batteries that have a higher energy density per unit volume compared to Apple batteries? Does Apple simply not fill all available internal volume and goes with smaller batteries because that is all it needs to be highly competitive on battery life?
I suppose my musings above come down to the basic question of whether, if it wanted to, Apple could somehow fit in a >5,000mah battery into say the iPhone 14 Pro Max without increasing the case size. If yes then that is something I would love to see. The 14 Pro Max is already a beast when it comes to battery life, at least according to various reviews, so just imagine how much clear water it would put between it and its major competitors if it had say a 5,500mah battery on top of all the power efficiencies.
My guess is that it all comes down to profit margins. Lower capacity batteries are cheaper (I assume) so Apple only does enough to stay reasonably comfortably ahead of the competition rather than trying to leave the competition in the dust. In my view that's a shame.