I go to aliexpress, and I see a number of 4" screens. Some even come with capacitive touch sensors mounted on top.
Yes, they are low-resolution by today's standards, something like 800x480. Still, they are available for those who might be considering to produce a really compact phone. Instead, they go to high-end coffee machines and the like, and to RPi tinkerers.
My hunch that the limiting factor would mostly be the battery. Modern radios and modern CPUs and GPUs consume more, and you don't want to market a very slow phone, or a phone that has 6 hours of daily usage worth of battery. And you can't hide as much battery behind a small screen.
Yes, they are low-resolution by today's standards, something like 800x480. Still, they are available for those who might be considering to produce a really compact phone. Instead, they go to high-end coffee machines and the like, and to RPi tinkerers.
My hunch that the limiting factor would mostly be the battery. Modern radios and modern CPUs and GPUs consume more, and you don't want to market a very slow phone, or a phone that has 6 hours of daily usage worth of battery. And you can't hide as much battery behind a small screen.