Board Thread:General Discussion/@comment-24755726-20150211193437/@comment-5629290-20150212074224

Since a lot of Gem powers seem tied to emotional states, I think Amethyst just has the personality best-suited for shapeshifting. She does what she wants, she makes herself into what she wants to be, she impulsively shifts gears all the time. Garnet is solid, unyielding, and only as flexible as is necesary to handle the situation, so she shapeshifts a little but not all the time like Amethyst. Pearl doesn't really do improvisation; she relies on consistancy to carefully plan her moves and changing the entire way her body is built is too drastic of a change in her eyes.

We have seen all three Gems shapeshift, however. They did it to change into their summer outfits for the beach party.