Usability.

Windows and Mac are both easier to use for the standard user.

Not at all true anymore for Windoze. Windows 7 was the last installment where that was true. Linux distributions are consistent. Once shown how the basics works, e.g., apt install or pacman -S and the general whereabouts of settings or software, it’s super easy to get them going, indefinitely. Even troubleshooting is within reach because searching the settings isn’t a maze within a maze (except for Gnome sometimes). Windoze keeps changing shit constantly, reinstalls uninstalled software, search algorithm is horrible and has Bing search results within the menu enabled by default [the fuck?], updates don’t indicate how long they’ll last, setting a default program often requires configuring it manually for every file extension, oh goddamn fuckers I have to stop typing because Microsoft pisses me off so bad.
Tabula rasa, if I had to teach a 70-year-old who’s never touched a computer before, to do so, I’d pick Linux every time. Consistency and customization is key.