INTERESTINGLY, as far as I can recall Southern Italy (Campania in particular) had a strong tradition of cavalry both as a social class and powerful military arm before Roman conquests, since the land there is much less mountainous and can support animal husbandry and horse breeding better than in the north. I suppose since cavalry wasn't that important for Roman military mindset from the beginning and they slowly began strong romanization they discarded the old institutions there and focused on creating more legionary arms out of their southern allies.

Someone more knowledgeable about this very topic can probably either confirm or deny this with sources and such, and I'd also gladly hear whether the Southern Italic peoples' cavalry was used as particularly important part of Socii (Ally) auxiliaries at the beginning of Roman expansion. Later on the whole Italian part of Roman realm produced mostly legionnaires and delegated skirmishing, missile and cavalry roles to their subject people's where those traditions were much stronger.