The problem with automatic daemonization is that there is no way to indicate startup failure: you just fire and forget the process in the background. If the process dies, there's no clear way of knowing whether it was due to an error in startup conditions (possibly as simple as a configuration error) or a runtime failure at a later time. In the first case, restarting makes no sense. In the latter case it might be a reasonable option.

With manual daemonization, the process can delay forking until it has ensured that its configuration is sound and it has the resources it needs. This way the parent process can indicate with its exit status whether the service was successfully launched.