Oof, that hits hard, but you're probably right: I expect there are more people who primarily (or even exclusively) use a smartphone or tablet than a general-purpose computer running a general-purpose OS.
There are libre mobile devices, but approximately no-one uses them, just like approximately no-one uses Linux on the desktop. Unless some large vendors start shipping Linux by default on all their devices, or the current mainstream OS vendors become really obnoxious and people go searching for alternative devices with Linux installed by default, that isn't going to change since people really don't want to have to do installs themselves.
It's a sad state of affairs, to be sure.