Because the whole creation is evolving to That Supreme Truth, Beauty and Unity consciously or unconsciously, through strife and struggle, through life and death, through wars and peace. Yoga essentially means Union with the Supreme Being Who is all these Becomings in Time.
For me all actions dedicated to my Highest Self that's one with the Supreme Self of the Universe is Yoga-the Yoga of Action. All seeking of integral knowledge and discovery of essential truths of anything and everything is Yoga-the Yoga of Knowledge. And when one knows the highest Supreme Godhead integrally, it spontaneously turns into the Yoga of Love, God-Love. Then one does everything not for fulfillment of any desires, not even as a right duty or work to be done but for the sake of Divine in himself/herself in total freedom and absolute delight. Nothing in life and the world is undivine. Everything can be transformed into divine joy, even the very substance and structure of matter itself. This is the Supreme Yoga integrating the paths of action, knowledge and love into Divine Love and its joyous expressions.
This Oneness and union with the Supreme consciousness and Conscious Being does not result in uniformity or homogeneous existence. It becomes a celebration of diversity and infinite variegatedness.
This is our supreme goal and our divine destiny.