Because even if we let Turner and Crabbe go, we are still left with close to nothing in our cap space. Our current bill for 2017 is $137M, you remove Crabbe and Turner and you are still paying almost $100M to your current players. CJ and Dame alone make $53M. Then you have Moe at $10M, Meyers at $10M, Aminu at $7M, Davis at $6M. Cap space will probably be $105M or so, even if you let Ezeli go (we will), we will at best have around $15M of cap space left in the end. It won't be enough to sign one of the top free agent players (and I am not taking Hayward or Griffin here but merely the likes of Ibaka and Waiters). You gain nothing.
I think teams would also take Crabbe from us without us attaching a pick. Dare I say I would expect someone crap to offer small assets in return. I think what is doable is trading Crabbe to Philadelphia for #36 pick. They won't get at shooter they need with their pick, have lots of cap space with hardly anyone to use it on and could do with a decent shooter. As for Turner, if Boston were not likely to land a big time free agent I could maybe see them offering one of their second round picks for him as they liked him a lot. It won't happen though.
I reckon we will trade Aminu and Davis for a pair of second round picks and call it a day.
I wouldn't mind if we were playing Anonuby, Hartenstein and Leaf a lot next season.