When I'm scripting, I spend a lot of time trying to reduce unnecessary coding. It would be great to have monsters wandering about, looking at things, etc, but it does take a lot of code to make that happen. As you no doubt know, the heartbeat script is executed every six seconds for every active creature in the module, including NPCs. Sometimes it amazes me just how much is going on computerwise on a game like NWN.
Right now, KTII doesn't have a lot of players, so the heartbeat script effects aren't as obvious. If KTII had 20 players online at the same time, each in different areas, the load would be pretty high. That's because monsters/NPCs activate if a player is in the area. If the area is empty, the creatures immediately exit the heartbeat script (it's still executed for every single creature object, except PC, but it ends quickly for inactive monsters).
Besides, what time I have available for the module should go to adding plots, reworking creatures/items/areas, etc. Monster AI scripting is undoubtedly the most complicated area.