For the life of me, Id never thought they'd do this. It makes room for Melo if they send him via sign and trade, but Chandler Parsons, he's a good player, but I don't think he's really head and shoulders above Gallinari or Batum.
And the rules regarding cap holds are not in Houston's favor. The minute one of Parsons's suitors put an offer officially to Parsons, that's his new cap hold. If any team wants to offer a starting salary in the $10 million range, that's Parsons's cap hold. Houston can than renounce their rights, and still move him via sign and trade, but they can't retain him without leaving his cap hold on the books.
If Houston wanted to create cap space, they could just cut Covington and Daniels, at no cost, and create the same amount as Parsons's option, which still counts as their cap hold, and then some.
So basically, it really only makes sense if they're trying to move him via sign and trade, unless I'm missing something.