iPads need to have some sort of bezel, else how are you going to hold the thing?
iPhones you can grip the sides, iPads not so much.
This. Phones are already a real trade-off between usability and screen size. I've reached (or perhaps slightly gone over) the minimum amount of grabbing space I want on a phone and mine isn't quite the sleekest model
iPhone 16 pro max is almost there with the screen size, also a two-hands device