Because decentralized organizations like the DAO are only one of a multitude of different things you can implement with Ethereum.
Scam tokens were never going to be the big driver of Ethereum success, official acknowledgement of it as a valid platform was.
This goes another step in that direction, particularly as it avoids clamping down on cryptocurrencies like Ethereum or Litecoin, which the IRS has deemed as property.
Initiatives like the Ethereum Enterprise Alliance are also contributing, so the more respectable it appears, the higher the price is likely to go due to higher expected future utility value.