Honestly, because I like that my user has a name, it makes me feel more comfortable during bug investigations where I enter the running docker container. BUT there is also a technical reason: The nobody:nogroup would be a perfect idea if you had the chance to log in to the shell. But unfortunately, the Linux Standard Base (https://refspecs.linuxbase.org/LSB_3.0.0/LSB-PDA/LSB-PDA/usernames.html) says it should have no shell assigned. So the user, nobody, is also reserved for NFS only.

Copied following answer from: https://wiki.ubuntu.com/nobody

Some misguided programs or guides suggest that this user should be used for untrusted program execution or handling untrusted data. This is bad advice. Services should have their own, dedicated, user account. Even on sites where NFS is not being used, processes run as user nobody or files owned by user nobody may grant far more privileges than expected, especially if two services have been misconfigured in this fashion.