Same as special slots, such as Spec or SG, are reduced according to server population, CAS should not be available until we hit X population.
The impact of CAS in lowpop games is simply not balanced, it has all the firepower from highpop (it may have less points, but the firepower is the same and it can have a huge impact. A banshee or a Napalm does the same highpop or lowpop).
CAS is one of the big things that makes lowpop so unplayable for xenomorphs.