can anyone explain why there is 8gb of memory that size, and Apple just can't stick 4 of those in an iPhone?
Correct me if I'm wrong, but you would require a completely different infrastructure to link these things together seamlessly. A single 32GB slice of memory is much more expensive than four 8 GB slices. That said, the 8GB iPhone uses something very similar to this. I once dismantled an old iPod nano and found the Samsung NAND chip. It was about as big as the first section of my pinky finger, from the tip to the first knuckle.
Infrastructure is the same reason why we can't just jam together a bunch of cheap flash memory to have inexpensive solid state storage in computers. I'm pretty sure the flash memory used in 32GB iPod touches can be used, however (in Macs at least, since it's HFS+ formatted), but then you'd have several separate 32GB drives/partitions.
I know it's a very simple explanation but I really don't know much about it.