[somepig]

POWER and Power (formerly PowerPC) are similar but quite different. PPC has been in embedded (but generally not mobile) for quite a long time, but even then, the cores are still hot, power hungry, and poorly suited for mobile.

[StillBored]

Because the designs predate the big push into extremely high efficiency processors. Like the big "server class" processors, the investment required to create a truly high efficiency processor is quite large. Small in-order cores with limited functional units, and lacking much of what makes a modern processor fast (vector units, specialty instructions/etc) can fool people into thinking that minimal clock domains/gating is sufficient to create a high efficiency design.