Yes because the Enigma protocol cannot accept USD, or DAI, so it requires an intermediate token. You can buy the ENG token with those other tokens but in order for the Enigma protocol to provide incentives across all platforms (not just Ethereum) it must have it's own token.
From my perspective it seems necessary. Why don't you think so?
RE: Is Steem finally headed to $10+? And the importance of the Enigma price rise (Enigma is the #3 fastest growing crypto)