the disc version had several expansions, including insect invasion. why is that not in the gog version?

I know this is months old, but in case anyone comes by and is deterred by this, it is simply not true. Both the Steam and GOG versions of the game come pre-patched to version 1.1 and include the Insect Invasion expansion by default. It just needs to be selected from the mod selection screen on the main menu.

And here I was expecting that you were going to complain that the radio drama was missing. (Which it isn't.) As someone who owns IC in physical form, Insect Invasion wasn't even a pack in!