Why aren't the keycaps engraved so that the light shines thru them and you can read what's on them?

That'd be nice!

Because there is no light behind the keycap - only an LED with a extension arm that reaches back to where the LED actually is located on the board. You'd have to re-design the entire keypad to do what your suggesting... and I'm not too sure it would be liked. I already get some complaints that the 6 button is too "brightly lit" - so we turn the default BLUE off until an action is done etc... by lighting them from behind we'd get more complaints than we get now... so we'd have to have an option to turn the text off vs. the button LED... now we're getting complex... and the complaints I'd get... phew... have to go jump off a building to silence the voices in my head...