Buster15,
Did the Gulf War, Afghanistan, Iraq, Iraq again completely pass you by?
Seriously though, I guess for exactly the same reason that the USAF decided to 'eak out' an even older airframe when they also had in service B-1's, B-2's and a large force of other Tornado like strike attack assets.
As some above have said, the ability to carry 21 x 1,000lb's or equivalents a long way, a bomb bay and pylons stuffed with LGB would have been extremely useful in various Gulf escapades, Storm Shadow, Brimstone, the list goes on and on. Add to that it's ability to act as an AAR asset as it dod for a few years, I remember a conversation with a 1 Grp AAR planner about the Vulcan tanker, expecting him to diss it. His remark? "if the VC10 or Victor fleet could give me the same availability I would be delighted!"