I believe that the journey is a big part of any experience, gardening included. Maybe it's because of my rural, agricultural background, but I don't think kneeling down over an aquaponics tank and running the water through my fingers would give me the same feeling as that warm, fresh soil in Springtime. The smell of it, the feel of the sun on my skin, the cycle of a growing season... it has a beginning and an end. That's all a part of the experience for me, the same as the end result- harvest.
Not to take anything away from aquaponics, I believe it is an excellent idea, and look to see greatly expanded usage in the near future, as I believe we should. I love reading about the ingenious homegrown systems out there.
Some of us, certainly myself, may just feel a little stronger ties to the soil, and the cycle of life.