Because you did choose it, somewhere along the way, consciously or not. The very foundation of our existence is free will, our freedom to choose. No one likes anyone else messing with his or her choices.
Non-acceptance puts us in a weakened position. We can't move ahead from a place we don't care for by focusing on our misery. I close with this quote from R. Buckminster Fuller: "You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete." Accept, create and move forward.
Change is constant,