Good questions. We're maybe not supposed to remember our past lives clearly or at all because it may distract us from our mission and learning lessons of our current lives.
It also seems that some people are first timers on earth and just lived in other galaxies and on other planets before. I met a lady whose name was actually Power like in the movie "powder". She was very pale and had to stay out of the sun and wear dark sunglasses. It was as if she wasn't well adapted to our atmosphere, but she had a tremendous energy and healing powers. I met her in a reiki class and the reiki teacher noticed her abilities and told me that her healing powers and energy were incredible and that she was on earth for the first time. She was very clumsy and different. He suggested that we should help her a little.