I'm sure there's a patch note somewhere or a thread with an official comment but it would be from years ago. The focuses used to be active on TLP's, then they decided to remove them until a later expansion pack. This may have been around the time Agnarr was launching, but I don't remember.
They removed focus effects on Mangler initially when they were trying to make it the Hardcore server with slower exp gains, increased exp loss on deaths, etc. Everyone hated the Mangler ruleset, it got changed, the focus effect thing just stayed in.
