So, spentak mentioned this above, but we originally considered launching a Catapult network and then launching Cache on it, but we didn't because Catapult doesn't support transaction fees yet and there is also no governance/staking at the moment.

If we used Catapult we would have had to make sure we ourselves had a stable network and somehow convince users to host nodes - all without harvesting and incentives. Token purchasers wouldn't have felt comfortable buying tokens on Catapult yet.

We are coding every day on Blockstart (which is using Catapult) and working also on nem2-sdk.