And randomised barons and mayors get the culture from...?
Then look at Hungary and say me where are the Slovaks? The Albanians? The Vlachs? Other local cultures who don't rule anything? (At least on later start dates Albanian should be there of course)
The province culture is a mixture between many factors. And Southern Italy was more influenced by Langobards then by Northern/Middle Italians.
There are quite a few cultures that aren't in the game (and there are Vlach in Hungary). And did the Langobards really have that big of an impact on Southern Italy? I'm genuinely curious because from what I can find the Langobards and Lombards refer to the same group of people, and the region named after them (Lombardy) is in Northern Italy.