I understand your argument. However, when I say popular I mean services that become staples in a smartphone app list. The obvious ones: first it was facebook, then came Twitter, then Instagram. These are services that damn near everyone with a smartphone knows about. Snapchat has become one of those. When you ask where? It's only obvious; around 90% of the smartphone market owns either Android or iOS. Unless an app is touted as a platform exclusive it is usually on both of the aforementioned OSs. So get those "staple" services on Windows Phone via their damn near infinitely deep pockets. They can continue to work on expanding market share, once they've wrestled into second place they can much more easily negotiate their exit from "extortion" from 3rd party devs.
A) So the Slippery Slope applies you just want to be the one to define the terms so you are happy with it
B) Nice of you to spend Microsoft's money that way
As far as I know... Companies are in business to make money. Windows Phone has been a loss-leader for Microsoft for quite some time. To suggest that they have "damn near infinitely deep pockets" ignores all other aspects of running a business. No company expects to continue with a product at the cost of financial ruin. What you suggest would hasten that breaking point where Microsoft walks away from the loss-leader that is Windows Phone and declares it a total loss.
As far as I know... Companies are NOT in business to make money for others while they bleed resources away at a loss in support of those non-reciprocal entities.
I'd not be happy at all to see Microsoft cripple OS support by draining resources off to support a never ending barrage of current and emerging third party services. I'd rather go back to Android on a Nexus.
Look how many users are in an uproar over Microsoft Apps being released to and receiving support on other platforms.
If Microsoft decides they will pander to social media, develops the OS around them and creates Apps for their services it is simply shifting discontent to another group of users who would want to leave the platform. Myself among them. I'm already cheesed off I can't use my people tile in any size other than small because I refuse to have the Facebook icon blinking at me after I already deleted the App.
I don't want my OS of choice to be run on such a stupid business model of giving in to populist pressures with nothing to show for it but a big hole.