Not counting your opponents graveyard is certainly a downside, but costing half the mana is a big enough upside to make up for this
For example, with Maelstrom Wanderer and a number of other cascade cards looking for free spells in the "Chaos Reigns" deck, I know I'll be adding in Rashmi, Eternities Crafter for more free casting
This puts serious constraints on us and is an obstacle we are going to have to overcome if we want to make a Sultai Courser deck work
An example can be found with the featured card above
Puresteel is great because it triggers on EtB not just cast, allowing Teleportation Circle and recursion to draw you cards in a pinch
While transformed, it even gains an activated ability that allows it to cause a wolf or werewolf to fight target creature for the cost of four mana, not just adding tokens to the battlefield, but fight-based removal as well