Because there are too many ideas and there are too many things I want to write. If I don't write down many things, I will slowly forget them, and I will feel regretful when I think about them many years later.
A large collection of various ideas, some of which are based on a passage, a photo or a story.
Or it may be a supporting role in a novel, TV series or movie that I have watched before. The scene may only have a supporting role for two or three seconds, but this cannot stop my imagination from running wild.
Update from time to time