Ossification is not brittleness or rigidity. It' is the solidification of a sound foundation. Without a working bone structure, you're left with an amorophous amoeba, not a functional organism of any higher order. Anyone arguing for the benefits of continuous modificaitons to the skeleton of an organism has the burden of proof.

From Sun Tzu: To fight and conquer in all your battles is not supreme excellence; supreme excellence consists in breaking the enemy's resistance without fighting.