I was working in Microsoft about 5 years ago and Satya's not lying when they say they tried everything to incentivise app developers. It was a big focus of the company at the time. For keystone apps they tried to partner with developers doing most of the work for them. For more niche apps they ran promotions for students and independent developers giving away free phones etc. But nothing was enough to get over the pr…
The report I heard back was that they treated it as an opportunity to try to sell us Office 365.
(The port never happened because the client's plans to roll out Windows phone to their staff fell through some time later.)