There were multiple discussed, and even working, versions of the original introduction to Cinderella, including scenes where we see the titular character with her mother, grieving the loss of her father, and Lady Tremaine making the acquaintance of her new stepdaughter. Ultimately, Walt opted for the final version above for a few reasons. First, Walt felt there should be a spoken narrator and he specifically wanted the voice to be that of a woman's (Betty Lou Gerson was cast, who would later go on to be Cruella De Vil). Second, he wisely knew that this film would deal with Cinderella as an adult character and how she continued to fight against the abuse that was inflicted upon her and would, ultimately, triumph over her perpetrators. He felt spending too much time on the background of that struggle would detract from the setup of how we first meet her and the action resulting from how she navigates her circumstances in the present. Lastly, the narration serves to explicitly state that Cinderella was "abused, humiliated, and finally forced to become a servant in her own house." There isn't room for someone to interpret that the abuse "was not that bad," or that she should've "tried to just leave," or any of the other weak criticisms people have for this film and abuse victims at large. We are told Cinderella is forced into this situation with no way out in the only home she's ever known from the time she is a small child, it is canonically stated that she is abused, and we see that she's grown up in this toxic family structure, being grossly mistreated by Lady Tremaine, Anastasia, and Drizella. This sets her up as the heroine- while her stepsisters perpetuate the cycle of abuse, she puts an end to it through building community where she can, never losing sight of herself, and continuing to keep hope alive. This prevents her from giving up, and ultimately leads to her salvation as her repeated attempts to leave her abusive household to attend the ball and be seen as a person in the eyes of her society finally become successful.

Then disappeared after Cas became Angel again

I recommend you strongly to read this excellent post about the whole nightstand saga

You’ll learn that (Is it really news for anyone at this point !) every single detail is deliberate

The Long Night Anniversary