Earlier this year, T-Mobile CEO, John Legere, took to Twitter to share his thoughts regarding Microsoft's failure to discuss arrangements to carry the new Lumia 950 and Lumia 950 XL smartphones on its network. This was in contrast to Microsoft's assertion back in October that its deal with AT&T was not exclusive and that it was in discussion with other carriers within the US and internationally.
Since then, Verizon has seemingly been disinterested in offering these flagships to its customers and even going as far as blocking the Lumia 950 family from connecting to its network. This effectively shutdown the option for customers to purchase unlocked versions of these smartphones direct from Microsoft, forcing them to consider switching carriers or other smartphone platforms upon next upgrade.
Further context to this situation has come to light after Uffern on Reddit was incensed enough to complain to the FCC about Verizon and its activation restrictions concerning the Lumia 950 and 950 XL. In the received response, Verizon stated that "there has been little consumer demand for Windows 10 Smartphones" and "Verizon has chosen to not carry the Nokia Lumia 10 in its retail channels."
The response then puts the ball back in Microsoft's court (referenced as Nokia in the letter) by stating that "if Nokia still wanted to make the device available to Verizon customers, it could have the device certified for use on the Verizon network through Verizon's Open Development program."
Ultimately, the question remains as to why Microsoft hasn't pursued certification for its latest smartphones. Microsoft did indicate back in October that it would partner only with carriers that were receptive to its platform. Whether or not this is a specific swipe at Verizon or simply byproduct of Microsoft's rebooted mobile strategy moving forward is up for debate.