The key reason I use a pseudonym is to be able to discuss in public, should I need to, candid opinions about things I would not broach in the workplace - politics, religion, football, national sports, which can be divisive in the workplace.
This way my personal opinions on touchy subjects, remain private and never at risk of being revealed to work colleagues, or cause any irreparable rifts.
I live in the UK. When Brexit happened, on the only occasion I have ever made an exception, I mentioned to someone in my team who was close to me, my position on the topic, and she was on the other side of the divide. This was after the referendum decision had been announced, and it did cool off our erstwhile warm personal relationship.