because many of the other factions were barbarian and they didn't have writing. (i' talking about BC). Also the history proofs that the romans were the most powerful and smart civilization in its time... i don't recall barbarian city north of Rhine, big and developed (with sewers, fountains, aqueducts...) as Rome.... I don't recall modern civilization to use laws and technologies, invented by barbarians...
The romans created history, which can be seen today. There is information, scripts, columns, which tells us the history. They created the foundation, on which the "modern world" is based, even to this date...
Also the mod is quite historical for all factions (buildings and mostly units). I don't see a problem with that.
And mostly, i'm sorry for the terrible off-topic.