LR save word in the stack frame

[void.cpp]

Hello experts,

I am reading the Systeam V ABI for PowerPC and have a question about
the LR save word in the stack frame.

The ABI says:

> Before a function calls another function, it shall save the contents of the link register at the time the function
> was entered in the LR save word of its caller’s stack frame and shall establish its own stack frame.

Here is my question:

Why should LR save word be saved in the caller's stack frame? Why not
just use the callee's stack frame?

v.c.