In reply to oggi: Doug's reply seemed pretty accurate and reasonable to me. I work as the Chief Officer for Mountain Leader Training, so am in a reasonable position to add a bit of detail. As has been pointed out, much of the background is historical, but we still need home nation boards for several reasons; dealing with the various home nation sports councils (who set targets for their own countries), dealing with home nation education organisations and funding streams, and ensuring that provision of courses is best able to serve local needs; by having Board members elected by the various stakeholder organisations.
At UK level we try to coordinate resources so that we don't duplicate effort, and to ensure universal recognition of the qualifications. We are working on siplifying the registration process so that people should be able to just register for the award rather than completing what must seem like virtually a citizenship exam to work out who and why to join beforehand!
We are aware that it all appears obtuse to the people who just want to sign up for a qualification and don't care about all the internal politics and are working hard to create a simpler interface. However, every step forward requires negotiation with a lot of organisations (government, National Councils, advisory bodies, etc etc) and also safeguarding and promoting the existing qualifications. I thought it would all be pretty simple when I took on this job 3 years ago, but I underestimated the task ahead! We are making progress though and you should see clear signs of this over the coming months on the Mountain Leader Training website (www.mltuk.org)