It allows you to push a lane without being there. That's valuable if you're playing against a team who is always grouping and can never really get that moment to push out your lane. It also works great on split push champions such as Shen because you can place the portal in the lane that you're pushing, then ult your teammate into the fight and the lane will keep pushing.
Kim Grin Un1 votesI love it on singed, especially against an AD top where I can rush raptors cloak. mmmm
Archon X1 votes
lets you push a lane without being there and gives great stats. I often get it on ap supports if I am not getting 
Gare Jordans1 votesYeah but 
is like the Bruiser's version of which is normally only built on AP supports.
Archon X1 votesah yeah sorry after rereading you were talking about non-supports building it. I stand by banner being better on supports, but no argument that zz'rot is more appropriate on bruisers.
Gare Jordans1 votesI completely agree. I love building banner on supports.