They're paying people to have the specific domain knowledge that can be applied quickly in emergencies.

I suppose it's a bit like being a fireman at an airport, the chances of having a plane need your services are I would've thought pretty rare, but you still need to be there and you've still got to be ready because you've got to react incredibly quickly if something goes wrong.

Can't have an airport without firemen even though an incident requiring their services may never happen, I guess companies feel the same way about corporate lawyers, HR departments and PR people.