The more I think about it, the more I think they are.
They were designed to stop people nicking your very expensive and brand-new alloy wheels, back when everything came on steel ones. These days every single car (give or take) has alloys, so unless you're running really desirable M or AMG wheels I reckon locking nuts are more hassle than they're worth.
How many times do we see people on here with stuck nuts, or lost keys? Is the risk of having your standard wheels nicked that high that we need to give ourselves the ballache still?
It's always a faff, trying to find the key and then transposing it across to various wheels when changing them, along with the risk of damaging the nuts themselves. I'm kinda thinking that unless you've got £3K worth of wheels on, you're better off running standard nuts all round.