With the lack of flagships and the coming of the Windows 10 Universal App platform, we've been in a holding pattern for over a year. The same goes for devs.
FB, Twitter, Vine, and many others ARE coming. I suspect Snapchat will come largely BECAUSE media uses it and it's a lot better to have multiple windows open on a desktop or laptop than flipping through apps through a switcher on a phone, regardless of platform. Station manager at big local iHeart station has said their company is demanding Windows 10 apps because of this.
This is the hidden secret to Windows 10. Businesses use Windows 10. Many businesses will LOVE the idea of mobile apps running side by side in a desktop because it's better for their business. Businesses drive advertising and subscription accounts for many companies.
You get Windows 10 into media, into other businesses that spend lots of money and any big app would be unwise not to come to the party.
It's not just about consumers, though the interesting aspect of Windows 10 is people ARE preferring to use apps over web browsers for things like Netflix, Hulu, etc (this WASN'T the case in Windows 8), but also about various enterprises.
The argument for HUGE media companies to move to Windows 10 centers around the ability to run FB, Twitter, SnapChat, WhatsApp, etc on one screen. I also expect a move to find a way to make your mobile phone and SMS show up too - regardless of the OS on the phone. The local ABC news station my father worked at for years and their parent media company are excited about this idea for their news broadcasts.
But we've taken time to get here. And, sure, there's a chance it won't work. But this is focused on Windows, Phone, and Xbox. And MS is working hard in the background to get all the major players on board, including the largest banks. They figure if you get the big players, the little guys will come eventually.