When you add a computer to a group in Active Directory, the computer does not know that it has been added to the group until a reboot happens. There are many obvious reasons why this is a problem. For example, you can't just reboot production servers at any time. Most organizations have some sort process in place for scheduling server reboots which in itself can be a time consuming process. When it comes to Windows Event Collection there are many reasons for adding endpoint forwarders to groups, especially if you are using Supercharger. For example, Superchargers builtin load balanced or distributed subscription feature rely's on group changes to keep forwarders balanced across the number of specified collectors. This is why Randy Franklin Smith of UltimateITSecurity.com designed and wrote KerbPurge.