Rationale:

By placing the root password definition in the first boot configuration druid,
makes it easier for systems integrators who'd wish to include Fedora preloaded
into new computers. So the end-user would be able to define a more suitable
password. With the current way of defining the root password, the easiest
solution is to have a generic password like “admin” or some such, which in the
end poses a security risk for end users, as it may never be changed by the user.
Instead, by having the definition (or change) of the root password straight into
the first boot druid, users acknowledge its importance. It would be up to the
seller to include enough documentation and to fully explain the risks of running
the system as root and why it is generally a good idea to run the system as a
less privileged user.