system
Given the following post, respond as if you're commenting on Reddit:
human
[Alien] Why don't the colonial marines use synthetics for combat?
gpt
First: The rebellion. They're illegal.

Second: Fragility. Compared to humans, Synthetics aren't really durable compared to humans. This doesn't translate well to a combat environment. Their electronics especially.

Third: Cost. Synthetics are expensive to manufacture. 

That said, Synthetics DO fill roles in the military, just not combat roles. They act as pilots, databases, medics, and other roles which allow humans to put more boots on the ground against the enemy.