Microsoft Windows has reigned supreme as the most popular operating system for many years. For a long time, there was hardly even a 2nd place. The installed base of Windows computers are not going to disappear for a long time (in the computer world, a long time is defined as a year or two) but the makeup of the world's operating systems is changing due to the decided shift to mobile devices.
If you look at the overall numbers of devices and their operating systems, it is reported that Google's Android operating system may just have passed Windows in raw numbers of users.
Analytics.usa,gov measures the operating systems used to access U.S. Government websites. It was widely noted in the news that access by Windows dropped below 50% for the first time ever.
Since most of the government offices still use desktop computers, I am guessing that these figures are pretty much skewed to desktop operating systems. Mobile device use passed desktop use back in about 2013-2014.
In addition, those companies that have mobile devices are not promoting them vigorously. The reality is that genealogy is years behind the curve in technology. In my opinion, this is due in large part to the demographics. But even if future growth is assured by the growth of the older population of the world, that growth is not making inroads into the younger markets who are married to their smartphones.