Why do system administrators set the taskbar to not show the date and time on a server?
That option is not one that is set by a system administrator. It is the default when you RDP into a domain-joined server. You can find registry hacks to change this default here: http://social.technet.microsoft.com/Forums/en-US/winservergen/thread/06df9377-9f58-4b39-a72f-9261ec2837ab