What annoys me is the fact that you can currently fly into the UK (from most places) with the larger dimensions. So for example a businessman flying in from the continent to the UK for a day meeting with only a slightly abnormal laptop case (as I happen to own *) will not be stopped and will be fine flying in. Unless he has had the time to measure it, he will probably not even realise that his case will not be accepted on the way back, unless he checks it in! (and just who wants to do that?)
* = mine happens to be 1.5cm too wide, but I would normally never have measured it, because I've always considered it to be tiny.