> Sounds kinda silly

Not at all. For example, you might do something on your own that you don't want confused with your day job, such as something political or culture war fodder. Look at the people being threatened that they'll be blacklisted for what they say about the Gaza war.

Also, some privacy threats (e.g., corporate data collectors) work by creating a profile collected from many different places. You might want to isolate different things in life under different names.