Families flying 4000 miles to another country have to considerably more advance planning to do then say a family 1100 from Boston. Disney could offer the best deal imaginable 2 months in advance in the UK and few would be able to take advantage of it. Also UK guests tend to stay 2 to 3 weeks on average where as American guests average around 1 week. In a nut shell UK guests spend more so they get more. The same principle works in Vegas. If you are playing $5000 blackjack hands all night the casinos will comp you much more than if you drop $50 on the quarter slots.
Right now Disney is following the same pattern that they do every year so this really should not be a surprise to anyone. PIN codes to select people and UK deals come first. If the numbers aren't where they need to be you will start to see AP, Florida resident and general public promotions until the resorts book up.