The person who made gearscore really fucked up. This is the sole reason why we have ilvls in the first place. Blizzard probably never put ilvl on items because it would cause people to care way too much about that 'stat' which is meaningless but since we ourselfs started using an addon for it it didn't really matter anymore what Blizzard did.
Now it's only ilvl this ilvl that and people are even more focused on gear which isn't a good thing in my opinion.