Probably based on the current (low) complexity of how the specific "national cultures" are unlocked.But what's the purpose in dividing things up by continent at all? Couldn't you just drop the continental cultures, and start with pure placeholder civilisations now, allowing every civilisation to make any culture it meets the technology and geography prerequisites for? Is there some game balance reason not to do that?
Not that this is a particularly big issue for me. I'm just...confused about what purpose it serves.
Namely, a lot of them have extremely similar prerequisites that sometimes are ONLY divided by the Continental Culture "sub-group" to begin with.
On the other hand, the division itself makes perfect sense, since the cultures DO go "Human -> Europe -> English", which is in fact LACKING a "Regional" (or more) step as of right now.
It's just that the current format ignores "Human" (except for "Neanderthals", by the way) and goes straight to "Continental", and then directly to "National".
But the idea supposedly is to make the entire path unlockable, even MAYBE going as far back as "unlocking Human" just like you now can unlock "Neanderthals" as a separate "lineage".