My friend Ben hit the nail on the head.
…the majority of iPhone/iPad/mobile users probably don’t even know what “multitasking” is. They can probably only think about the one application they’re running at that very moment. Multitasking to these people would mean running out of processor power and memory, not realising it’s because they have 3 apps churning away doing their thing and only noticing the impact to the experience of the one app they’re focussing on right then.