Why did Glock add a pin to the 19 &17 Frame.

[sgtb]

I noticed that Glock is now making the 9mm models with 3 pins in the frame instead of 2. My 19 I just purchased is of the old style but 3rd. generation. Why did they do this?

[lastevolution]

It was for economic reasons. Put three pins in all of the frames, instead of having only G17/G19 frames with two pins.