Arduino Due (released Oct 22, 2012) Compatibility

This makes me wonder: Are ARM7 processors in smartphones (like the one in the iPhone) somehow designed for extremely low current draw? Shouldn't they consume more current than a 84-Mhz SAM3X would... As in, how do smartphones still get such long lifetimes while the processor is handling presumably a LOT of instructions, and also additionally using display, graphics driver, Wi-fi, GPS, etc.