And so continues the spiral as six months later they will take the benefit away as no one uses it.

I wouldn't be surprised if BA make a decision not to open a First lounge in the south terminal due to the reduction in Gold members using lounge facilities, either because club lounges have reached capacity, they use the priority pass lounge, stop flying or avoid Gatwick. It's a self fulfilling prophecy and it could be argued that the reduction was a consequence of the shorter opening hours.

I have heard of train operating companies do similar things when they cannot get permission from the government to close a route. They will reduce the service frequency and timings to make it very difficult for commuters to use and then re-apply to close the route down a few years later claiming lack of passenger numbers. I think the Primrose Hill Station close to where I live suffered a similar fate.