#2 WWE didn't need him this week
Did WWE really need The Fiend this week?
Think about it this way, between WWE being stuck in a state of limbo due to planning for WrestleMania season and trying to keep The Fiend relatively fresh, it makes perfect sense for the company to simply not use him. In fact, doing so gives the company a lot of booking options going forward and creates some very unique booking situations.
A little more on that later, but what would having The Fiend on this week's edition of Friday Night SmackDown really accomplish? Sure, it would have been a great chance for him to showcase some of his awesome parlor tricks or even add another interesting layer to his lore, but shouldn't WWE be saving that stuff?
Seriously though, WWE did not need The Fiend to further storylines in any way and would have just wasted the characters presence. Beyond that, WWE's original plan with The Fiend was to save him for special occasions, which could be what the company is starting to do now that he's established.
In the end, The Fiend didn't need to be there. There was no purpose that he could have served and probably better for WWE to start making him a special attraction again anyway. At least that way, it's always a surprise when he turns up and WWE can find new and interesting ways to explain his absence.