Comment by CoolestBeans

Because for a lot (most?) people their iPhone is their primary and only personal computer. I also want a smaller phone. I bet Apple designers would love to sell you a smaller phone. They've certainly tried with my beloved and retired iPhone mini and the same size but thinner iPhone air. But the market keeps rejecting it because it's not just a portable companion to some other computer, it is the computer. If you're doing all your work on it then you need more real estate. Aging populations across the globe probably need more screen real estate also for bigger text.