Speaking for myself, I retired my last desktop system a few years ago. But I have nearly 10 mobile devices in the household, mostly consisting of smartphones and tablets. All run iOS.
I wouldn’t call desktop systems and OSes a “dying business”, just a mature, commoditized one. I work on big databases on my home desktop system, and even for general browsing, the desktop computer is scads better for anything that isn’t inherently mobile (e.g. GPS) or needs a touchscreen.
Besides that, businesses live on desktops and laptops (which are often used as desktops. Mine at work is pluigged into three monitors, and a keyboard designed for grown American man hands). Microsoft still makes lots of money and lots of profit, and will do so as long as they can hold ontothe enterprise.