Normal NPC countries troop count.

I rarely play against normal NPC cause it offers negligible challenge but now I notice that NPC cities stop growing after 15 troops, in all NPC countries. Is this normal, was it always like that ?.

If yes, maybe remove this restrain ?. It is already boring that NPC countries don't seem to build any mechanize units, at least in my game, it is day 31 and I don't even see an artillery.