The reason to waive pierce and get him back at the MLE,
1) keeps the c's well enough below the apron to attempt a josh smith, al jefferson sign and trade, etc
2) save wyc serious money, 5.33m of the contract value, plus (penalty rate) 2.75*5.33m, as the c's likely to be in the tax. Thats about 20 million dollars wyc saves, which his entitled to try and save, he certainly hasn't been stingy