alt Hacker NewsIsolation from the main system, other services, and other dependencies.
Easy to migrate to new system.
Easy to upgrade and downgrade. When a new version causes an issue just restart it with an older version.
One directory to backup and restore that contains all the services and their settings.
A single binary accomplishes most of those things just fine. Only thing it doesn't get you is isolation, but you can isolate things if you want even then (for example, FreeBSD jails are dead easy to set up).