Id blame AT&T more than anyone. If AT&T doesn't think the phone is going to sell well, they demand exclusive deals like this. Microsoft has no choice really
You can't blame AT&T here. Legere appears to be a giant tool. He is jumping on Microsoft for an AT&T exclusivity that doesn't exist. He says they'd carry the devices, but they're exclusives, even though AT&T hasn't made a sound about carrying the 950 XL. When people pointed out articles that said that AT&T's 950 offering wasn't exclusive, his response was, "you shouldn't have to read it there, Microsoft should make it known." He didn't even address that he was wrong about the exclusivity deal, nor did he show any real interest in having a dialogue with Microsoft. He just made half-hearted insults every time he was told he was wrong on the matter.
The fact employees try to shift your freedom to purchase with loaded opinions at all is pathetic. They should just do what they are paid to do and sell a product without fluffing you into a decision, not act like calling the shots is everything.
Except that's often the training the employees get, I imagine. When I got my 920, the guy I bought it from flat-out said I knew more about it than he did. When my sister got her 822, it was the same story. When she got her ICON, the guy almost sold her a 928 and didn't even know it (my sister asked and I verified while he had stepped away from the counter). It's THEORETICALLY an employee's job to objectively listen to a customer's needs and make suggestions based on them, but my experience is that even as a now-casual observer of the smartphone market (I was pretty into watching it a few years back, around the WP8 time), I can basically stroll into AT&T and legitimately feel that I'm more educated than the majority (if not entirety) of the staff on the overall information related to the variety of phones they have. And, because of how I look at the stuff, what I don't know I can gather reasonable hypotheses on in a hurry because I actually know what those specs on the papers mean.
What you often get with a carrier store (especially one of the second-tier ones that have dummy phones, not live demo units) is a bunch of folks who know the iPhone, maybe the Galaxy devices, and if you're lucky, a couple of the peripheral Android options (like an HTC One or Sony Xperia). Why bother remembering the training (and why even have it) when the number of Windows Phone customers is probably rivaled by the grandparents wanting flip phones?