For most people computers are just the same as cars. People want a car that will drive them from place to place, are easy to refuel, easy to operate, and can be taken to an expert for anything difficult or that requires specialized knowledge. Same for computers. Most people want a computer to navigate the web, install the apps they are used to and that their friends use, is easy to operate, and can be taken to an expert for any involved work.
Even the friendliest of Linux distro don't check all those boxes. You cant get ready support from a repair shop, many of the apps are different or function differently, and it doesn't receive all the same love and attention from major third party developers as Windows does.
Most people could learn to use Linux; it's not that hard. Most people could learn to change their own oil. But for most people, it's not worth it. For most people it's not the journey, it's the destination and cars and computers are just tools to get there.