Well, you can't very well expect a speed camera to carry out a breath-test on every passing driver who might be drunk. You could just as well say that it's wrong that bank robbers who don't speed don't get picked up.

What annoys me is when they don't clearly enough indicate the limit. The only time I've been done for speeding was on a local road where there is a stretch which is 40 mph in between a pretty well identical stretch that is 50 and another that is National Speed Limit (ie 55). It is indicated, but only when you are entering it, and it's easy to miss the small sign.

But I should have been looking more carefully.