I use throwaway account for a few purposes:

* People cannot trace which dumb things I talked about in the past to use ad hominem on me. I felt disgusted when attacked by ad hominem. Without chilling effect of being dug from the past, I get more freedom in expressing opinion.

* To stay anonymous in a reasonable way, in the sense of preventing people from profiling username. Reading someone posting as 'anon314' or 'throwaway2021' would feel different from someone as 'hiimelonmusk'. It would leave no remark in the back of one's mind.