Because the watchlist is more accessible, being a single clearly visible button that defines if it is added or not. Otherwise, why have a watchlist when you could play the content for a few minutes and have it saved in “continue watching”?
My change conveys the same behavior, but with the added advantage of not having to constantly re-add content after viewing it. Taking into account that the watchlist can now be filtered, it could even be separated by “viewed” and not.
It is to group multiple functions to a single list that is easy to access and add content. My mother would have no idea how to add her movies and series to a playlist, while the clearly visible “watchlist” button is easy for her, but frustrating that her movie disappears after watching it.
It’s like the change that was made in “continue watching”, which was decided that it was more feasible for an awake person to press the continue watching button, than for a sleeping person to do so. In this case, it is more likely that a person who wants to remove content from their list will do so, than that a person who wants to have it on their list will have to re-add it.
