Medalion on Vengeful Spirit?

Hey guys I was recently playing a hard-core support as VS and when I looked at the (terrible) suggested items, I thought of replacing a Ring of Aqueila for a Medallion and it turned out amazing.
First of all it gives more armor than a RoA, and the mana regen scales, and the active ability plus your "W" is awesome.
I got a question, why won't more supports get a Medallion? I'm going to try to incorporate this totally awesome item into more of my games most often, especially when I play support.

Medallion of Courage is pretty expensive, and doesn't provide very much survivability. You could get two Bracers for roughly the same price and be much better off most of the time as a support hero. Vengeful Spirit also has low INT and a low INT gain so she the static mana regeneration from Ring of Aquila is usually better than the +50% mana regeneration from Medallion.

Also, most supports can't utilize the -armor nearly as well as Venge can, since Venge has another -armor spell ( Wave of Terror) and better damage (Command Aura). Usually, the only heroes that will ever buy Medallion are those that have a -armor spell (Venge), high physical damage (Lycanthrope), or both ( Templar Assassin). For other heroes, it's simply not very effective.

TL;DR: It's expensive (for a support), provides very little survivability, and most supports don't have the damage/skills to utilize it very well.