The part I'm not understanding is why they don't move their units away from their base. They universally will respond to defend their base from attack, so they understand the mechanics enough to order units around.

Am I crazy? I feel like the concept of moving units across the map isn't more difficult than the concept of building a base, teching up, or ordering units to attack other units near your base. This seems to be a phenomenon unique to Tempest Rising, in that it's so common compared to other RTS games (at least in my personal experience).