What is it with B-lister parties?

This is very common in Ireland and has been for a long time, immediate family and close friends are invited to the entire ceremony and meal and more distant relatives and maybe friends of the Bride and groom's siblings are invited to the 'afters', which is really just when the band and DJ start. These people are not expected to R.S.V.P or to bring a gift, they just come for the party and to enjoy themselves with everybody else. Most people don't get offended as this is how its always done.