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 problem of the lack of an initial user base.
Most Windows phone owners I know (myself included) loved the design (hardware and software), the customisability, etc. but the lack of apps ultimately made us move to another ecosystem.
Most Windows phone owners I know (myself included) loved the design (hardware and software), the customisability, etc. but the lack of apps ultimately made us move to another ecosystem.