Hello @bastibe
I am currently mostly running Windows, mainly to get access to Affinity Photo and a few other programs.
I could have wrote myself this sentence. Last year I have even bought myself a licence of Affinity photo, which I consider more feature-rich than GIMP 
I suppose the success of Windows and Apple is simply due to the huge amount of professional softwares for end-users in many domains (CAD, GIS, OFFICE, GRAPHICS).
Once in a whiile, over the past decades, I have tested Linux through VirtualBox or on a dual boot setup (mostly running Kde desktops) but in the end I have always ditched Linux in favour of Windows (please, don’t shoot me for this choice…).
I am truly amazed at the huge progress Darktable has done these past 2 years though and, thanks to Blender, Krita, Digikam etc, it is less and less “necessary” for everyone to choose Windows and Apple these recent days, IMHO