I suppose that makes sense.

But from a cost standpoint, it would make more sense to have onfi/toggle interface on the phones/tablet/etc pcb and let the SoC do the NAND managment. That way you have cheaper NAND and i suppose better selection on the market.

It is managed NAND meaning that it has the controller and interface built in. Overall, it is also a smaller design for mobile devices such as phones, tablets, GPS, etc. UFS is like the next gen of eMMC and both use less power than standard SSDs.

Why dont SoC manufactureres and NAND makers move to pci-e entirely ?
You have much better speeds, much much better random performance and an already known interface.

Is eMMC/UFS less complex or uses less power ?