Board Thread:Theories/@comment-27441457-20151225042055/@comment-25322628-20160608012506

Another possibility of the hardening and crystallizing variations between the shifters is due to a lack of imagination and creativity.

Annie and Reiner only use theirs for combat and defense purposes.

Eren, once he obtained his hardening power, is able to apply it in a creative way, such as when he used it the first time to save the others from the fire and later when he created the guillotine.