That just encourages using minimal evolution changes, even if most of the change you would be doing is for flavor.

For instance, if I want to turn into a scorpion, I would turn into a quadraped, add an extra set of legs, add a limbs for arms and cap with pincers, add a tail, a stinger on the tail, and poison on the stinger. Perfectly reasonable, flavorful thing to do, yet if I had to pay for each evolution from my daily limit, idiotic. I would be spending irrecoverable resources on fluff. I think fluff is good for role playing, but it shouldn't come at a high cost.