I don't think the term "British loyalist paramilitaries" is too accurate. Britain hasn't ever included any part of Ireland, and though they've friends in the BNP I'd doubt if many of the people involved in the loyalist paramilitaries come from Britain.

As for Rob Dale's question "Are the members of the IRA holding their weapons so that they can protect neighbourhoods from rioting mobs" - I'd say that is in fact the bottom line. I'd put it more that the IRA doesn't want to lay itself open to the accusation of having given up its ability to protect neighbourhoods from attack.

And there's the symbolism of not having surrendered and being undefeated and that. And I'm sure there are a lot of other factors too, including holding together and holding in check people with different views, some of whom might not go along with a decision to press ahead with decomissioning until a lot of things have changed at any rate.