They can be very handy for context, or even fun. For example, I have my "Galaxy Note 20" flair on /r/Android so anyone seeing my comments can know I am speaking from a Samsung phone perspective without me having to state that each time. On /r/nba people have their preferred team set as flair so others can shittalk back to them based on what team they follow, which is a lot of the fun of /r/nba.
There are many more examples in the different subreddits I would frequent, but regardless, I would definitely like community-specific flair options on the Lemmy instances. For example, the option to have your preferred distro as a user flair on !linux@lemmy.ml