Windows 8.1 mobile is still used by more than 75% of the tiny fragment of the market that uses Windows Mobile devices. Windows 10 mobile is at something like 15%. Largely this is the fault of Microsoft for cutting off so many loyal fans with older devices from receiving the latest versions of the OS. I'm aware there are valid reasons for this in some cases, particularly older budget devices with very limited processing power and RAM. But still, cutting off so many people and devices from supported updates so quickly did nothing to help their cause. They needed these people as evangelists for the platform, not feeling hopelessly abandoned by a company desperate to gain market share so as to gain app developers.