This has always been the case. Unfortunately for Phoenix, other teams are reluctant (right now) to give up 1st-round picks and/or players of value for Crowder.
Crowder needs to be a final piece on an already contending team. Even then, he is a solid starter/role player, not an all-star.
The amount this deal has been discussed in the public without getting done makes me a bit pessimistic. Rumors that Phoenix floated details of the deal to entice better offers, especially from those in contention with Milwaukee in the East. Not that it can't happen still, but this whole thing has been strange.