Perhaps I'm totally wrong, but...
Pins are made out of G10 because it's light yet very strong. I highly doubt "ease of replacement" factored into the picture. Yes, G10 pins are far easier to machine out than a metal pin. Then again, when replacing a metal pin it's much easier to heat the pin to break down the glue.
As far as the G10 pin "protecting" the joint during a fall... Huh? Have you ever tried to break a G10 pin? Clamp one in a vise and whack it with a hammer. I guarantee you they're stronger than you're describing. If an "accident" occurs that breaks the G10 pin, I'd be willing to bet there's going to be more repairs needed to the cue than just a new pin.
The typical "problem" with G10 pins is this: G10 pins can only effectively be made into large threaded pins (3/8-10, Radial, etc.) which screw into wooden threads in the shaft. The raw G10 material is quite abrasive and over time it will grind down the inner surface of the wooden threads causing the joint to loosen up. Some remedies are wax or thin CA on the G10 threads.
G10 pins are no more "premium" than stainless, brass, or aluminum.