Agreed. I suppose they are considered an effective but crude measure to increase downforce + efficiency but that f1 engineers will have many other methods of achieving a similar result if they were banned.
I am sorry if I was not clear enough anout the 'cheat' comment. It was made simply because of the recent attention there has been on flexible surfaces which, to me, highlights the difficulty in enforcing aerodynamic rules. A ban on gurney flaps is easy to enforce as they are detectable to the eye!