Um... because it's Blizzard's stated intention that socket bonuses should be a decision and not just extra stats on the item that you will always get anyway?
Several people have mentioned the sudden lack of spirit on T10 sets. But what strikes me as really bizarre is the color of its sockets
It has probably been mentioned, and I haven't payed close enough attention, but I was shocked to see the five pieces had only 1 red socket between them, and 3 each of Blue and Yellow.
I can sort of understand the blue gem on the head, the most popular meta requires 2 blue, and in the past, when I might have considered a helmet without a meta slot, having a blue gem in the head meant less regemming when swapping hats.
And I understand Blizz's dislike of items with all gems the same color, so RB, RY and RBY socket collections are understandable.
But why are our legs YB? And our gloves are blue, and our shoulders yellow. It's as unexpected as finding a small amount of defence or agility. All of our socket bonuses are pure spell power, so it seems obvious to me that they expect us to want to stack spell power, and they intentionally chose socket colors to sabotage it. Is it "Just to make it interesting?"
The legs are the worst offenders, luckily I've already decided that, unless they drop from VoA they are the last piece I'll spend badges on. I'm using Leggings of Woven Death and Onixia25's helm as pieces I'm swapping in and out while I try to navigate the path of breaking my 4T9 and building my T10. It's quite possible I might never get the T10 Legs, at least not while there's anything else I want purchasable with badges.