Keeping any kind of tank is a lot like gardening.
If you think about it, nurturing life is what we are all doing. People can say they like the beauty, or the challenge but I think the primary human desire here is nurturing life and making things grow healthy and strong.
I live in a cold climate, my aquarium keeping gets pretty focused come winter, that's when my projects get underway. In the summer, I have bikes and I used to tend the garden at my parents house, I don't have a garden anymore though.
But yes, fish tanks are beautiful and challenging. They are a lot like gardening, I think both are borne out of the same desire. For me I know this is the case.