The issue is that if you want to communicate with the outside world you need to create a network bridge, which only a sufficiently privileged user on the host s

The issue is that if you want to communicate with the outside world you need to create a network bridge, which only a sufficiently privileged user on the host system can do. An unprivileged-user docker daemon would be limited to either communicate with an isolated network namespace on the parent side or do userspace forwarding of network traffic. Or it would require a privileged helper for the network parts.