Because they aren't always performing a PUBLIC duty, it's often totally different.
You can try and apply the same ideas, and sometimes it might work, but it's likely to have a more direct impact on peoples lives, than whether Mr X knocks out 47 units a month opposed to 38
Look at Priors example of handing out parking fines. "get 40 a month or you're going on a 3-month warning, then you're out". So he gets 40 a month to make his target. The majority of decisions in the public sector would have direct impacts on peoples lives, whether that's through targeting nurses for quantity of patients seen, targeting teachers to get absurd results out of students, etc, etc.
I totally agree with the competition idea, with you on that, it needs to be a factor where possible, to rid the useless people
but do you realise, taking just one example here, how short the country are of secondary maths teachers? Let alone good ones
and why? What can be done to reverse that? I don't have the answers by the way.
I'm not in my job for competition or to become an over-paid, target-driven manager milking all my colleagues for what they're worth - that might work on a production line, it doesn't mean it would work everywhere else