A large fraction of the employees of corporations and other organizations need laptop or desktop computers: it would be impractical for them to use tablets or phones instead.
Only a very small fraction of those employees use any OS on these laptops and desktops except for Windows, and that small fraction is concentrated in the computer industry, e.g., Google and Oracle (if they are in fact mostly non-Windows; I don't know for sure) which means that the monopoly is even stronger in the industries other than the computer industry than the global numbers would suggest.
Only a very small fraction of those employees use any OS on these laptops and desktops except for Windows, and that small fraction is concentrated in the computer industry, e.g., Google and Oracle (if they are in fact mostly non-Windows; I don't know for sure) which means that the monopoly is even stronger in the industries other than the computer industry than the global numbers would suggest.