Why do the home nations get 50% of the sets in IFAB, the rule making body for association football? Canada does not get 50% of the seats in meetings to change rules in ice hockey, and the United States do not get 50% of the seats in meetings to change the rules in baseball, so why are rule changes in association football decided 50% by the home nations and 50% by FIFA.
As with a lot of things, historical reasons. The home nations created the rules for association football (the IFAB was founded by the home nations in the 1880s) and haven't yet given up that power. There isn't a deeper reason as to "why" - inertia is a powerful thing, and until there's an actual practical issue it's not worth anybody kicking up a fuss.