Because our forces always exhibit a "can do" attitude, the public, in their ignorance, still think we have substantial, well armed Army, Navy and Air Forces. It needs a prominent politician, backed by extensive media coverage,to make the public wake up to the parlous state our defence is in.
My personal experience is that those I talk to on the subject have absolutely no idea of the truth - they are shocked when I tell them of how little we now have.
Of course, it's in the politicians' interest to keep it hidden.