For every previous version of windows you typically bought a new licence only when you purchased a new PC.
The fact that MS allowed upgrades to Widows 10 on old machines should not have affected their revenue to any great extent, those machines were never going to have a paid upgrade anyway.
10% of Irish people are redheads while about a half carry the gene apparently. I'd be willing to bet the dark haired brother has forearms covered in freckles