My starting motivation was philosophical and academic interest. I was curious how it affects the mind. Then I did it because it seemed so hard to do, mind seemed like a buggy device I had no control over. I also had self improvement goals at some point. And feeling balanced is a good feeling.
But there is no way I can justify the amount of time I spend meditating with any of those. Meditation teachers say that first you start to work with meditation, then it starts to work with you. The whole view of the world changes.
I'm completely secular humanist but meditation has turned into spiritual practice. If I worship something, it's this moment. Asking why I meditate is like asking why people go surfing. Staying in the moment and balancing on the wave between the past and the future is not a activity you do for gaining any other goals. Being alive and experiencing the raw existence is something you sacrifice other things in your life.