Who, exactly, would we be targeting to use this space on?
Without a target to acquire with the space, there is not great advantage to dropping way below the cap.
Yes, it allows you to take in salary in trade without having to send matching salary out. But that's rarely an impediment if your roster has multiple small and mid-size contracts because you can usually find a third-party to facilitate moving parts around.
The negative of going way under the cap is that it then 'caps' you on how much you can spend on talent. You can only buy your way back up to the cap. If you stay over the cap, you can trade contracts to stay over, and maintain a 'talent budget' all the way up to the luxury tax threshold. The tricks are to (a) not go over the LT threshold and (b) to maintain that roster with a portfolio of tradable pieces.
Obviously, a contract like Wallace's is not what you want. But most of Danny's other contracts are fairly movable.