You'll see in the long run. SBD will be the stable form of payout. Without a stable currency in this volatile crypto wild world, it's not usable by the marketplace as a medium of transfer (exchanging goods for SBD, etc). And it looks like it won't stabilize until STEEM is much more established.

And I just realized something... if we suddenly decide not to base it on 1 USD, we could anchor it to something we know has stable value. But USD is the standard in the world, so there's no reason to look for that other thing just yet. The beauty of the price feed is that if all witnesses agree, we can always choose something else. But since SBD is still relatively rare, it can't perform this function yet. That's my take on it.