Hi Jenna, for me, it's to relax, stretch, and get a decent workout. More of achieving a zen state than anything else. Before I started Aikido, I had already done a number of different martial arts as well as competing in intramural boxing in the Navy. I already knew how to fight.
Aikido appealed to me because of the nature of blending, relaxation, and harmony. I have an underlying diagnosis of anklyosing spondylitis, and so flexibility is real important to me. I've probably gained about 40% flexibility from Aikido, and enjoy the workouts. I've lost weight, increased stamina, and enjoy the people who train Aikido, most with a very similar mindset.
I also do yoga on my days off from Aikido just to keep moving, and Iaido at times to just practice and improve my focus/concentration.
At 46, I could care less about fighting. I don't watch UFC or MMA with any regularity (maybe once in a blue moon if nothing else is on), and couldn't even tell you which UFC fighters were good or not.
I care far, far more about RELAXATION, stress reduction and release, flexibility, and achieving a more zen like state.
YMMV.