Backup, control and recovery:
BACKUP - the server has daily external backups, the workstations don't. As the profiles are stored on the server they are included in the backup.
CONTROL - as profiles are stored in one central place they are easier to administer and maintain.
RECOVERY - when a workstation dies I find most of the time is lost restoring settings - not re-installing software, with roaming profiles the settings are restored automatically.

I've searched for single logon - loads of hits but nothing that does the job.