POS only significantly reduces the hasing power needed, you still need a p2p network for a p2p currency to work don't you?
P2P network does not mean mining. If everyone has a wallet with connected peers and does not mine, the P2P network is still established.
Difference with the POS is that you dont need to hash for it, but rather be lucky. Therefore you dont actually "mine" the coins and thus dont need pools.
At least thats how i understand it.