Comment by MarekKnapek

Yes, Docker is weird. We already have a process management thing - it is called an operating system. But processes are misbehaved sometimes. They are not configurable enough, what if two processes want to listen on port 80? What if two processes want to save stuff at /var/abc.txt? And so on. In this case Docker might have a point. Otherwise it is just saysadmin's lazyness.