The root cause is the ridiculously small private address space in IPv4. Conflicts have a non-negligible probability. You might even want to use a container on the train, so the daemon is not the root cause of problems in this case.
Using IPv6 would have reduced the probability a lot. But the excuse for the last 20 years has been, why bother with learning something new as long as "it works for me"... (I don't claim I would do differently.)
Using IPv6 would have reduced the probability a lot. But the excuse for the last 20 years has been, why bother with learning something new as long as "it works for me"... (I don't claim I would do differently.)