Countries in the EEA but not EU (e.g. Switzerland) tend to have bilateral agreements with the EU which cover most EU laws, so I think legally it's often easier to group EEA together

E.g. EU enforces free data roaming for cellphone providers, but many providers allow free roaming to Switzerland and the Nordic countries too - not sure if it's just practically easier than trying to geofence those areas into a different tariff or if it's legally too complicated, but I'm fairly certain they don't do it out of the goodness of their hearts.