If they can do it, good luck to them! There is still a percentage of the Service that can just go off and do sport rather than work, that can take weekends for granted, strictly stick to office hours and - believe it or not - have refused to be called in out-of-hours. But thats another issue...
If they can get away with it and nobody can see the low 'return' well...
What does annoy is when Bloggs spends 6 months away bobsleighing or whatever, to have 'represents the UK bobsleigh team' in his ACR as a, say, rigger. It's less prevailent now, but national representation used to be a good way of getting promoted - so all the RAF got was a cpl bobsleigh team member who occasionally does rigger stuff.
I say keep it if thats what people want, but they shouldn't benefit at all professionally - in fact, it should be a neutral point.