Why would they?
Northern Ireland isn't part of Britain; only the United Kingdom
(Squidlipps Anyway, so how's your sex life on, Sat 5 Oct 2013, 6:05, 3 replies)

it's part of Lesser Britain
Great Britain is the larger Island to the east of Lesser Britain comprised of England Scotland and Wales.

Lesser Britain and Great Britain are part of the British Isles along with numerous other smaller Islands like the Isle of Man, Thanet, Dogs, Sinclair etc.
( buffet_the_appetite_slayer ٩(●̮̃•)۶ jacked in to the ICE on, Sat 5 Oct 2013, 8:08, closed)

Balls
"Lesser Britain" is that sticky out bit of France at the top. Ireland isn't Britain.
( Invisible Wizard - 9th Level Pissant, Sat 5 Oct 2013, 18:45, closed)

BAM, facted.

( BraynDedd Natasha Kaplinsky's labia majora, Sat 5 Oct 2013, 10:02, closed)

^ This.
The United Kingdom of Great Britain and Northern Ireland. "Britain" is generally accepted as short for Great Britain, which excludes NI (apart from in the Olympics, I believe).
( monster munch person, man, woman... camera... TV?, Sat 5 Oct 2013, 21:27, closed)