The movements we practice, even in isolation, are difficult to perform correctly with good power, speed, and posture.  Putting the movements to imaginary but spirited use in katas ups the ante further with greater focus on timing, distance, rhythm, and agility.  In kumite sessions, awareness, reaction, and strategy are added to the mix (along with a healthy threat of “negative feedback” for any deficiencies).  Karate is at the very least a training method, a crucible even, for developing physical and mental skills for fighting.