ANstar is correct, I'm afraid. Those figures are extremely out of date. Air 2000 was bought by First Choice in 1998, although the final rebranding of the aircraft didn't take place until 2004. And BA do indeed operate the A319 with 3 crew, LGW for the last three years and LHR since Nov.
Why do airlines put on more crew for service duties, but don't want to do the same for the safety of the passengers?
Because it's about money. Airlines used to be able to charge lots for those extra services and therefore were happy to pay for the extra crew needed to deliver them. But people don't want to pay all that money anymore. Premium traffic across the world has nose-dived leaving airlines looking at ways to cut costs and wondering why they need so many crew on board each aircraft. It's not right, but that's the way it is.