Right, and to be clear, I am addressing the scenario from the Roman perspective, not because I approve of it or whatever. Additionally, I am highlighting the notion that in order to mass produce written law and the other things necessary to successfully export a culture on massive scale over large distances, you actually do need a large population of literate slaves, which, if you're going to have slaves, is the last thing you want.

Edit: to clarify, slaves are necessary to export culture because someone has to transcribe all of the books and laws etc.