The General Failure of Government

It would seem to me that, across the course of the last couple of hundred years where political economy has really come into its own, and even in the history of humans before that, there has been a general failure of governments to do what they intend to do.

It would also seem that people in this age expect a lot of government - if something goes badly for them, then they expect the government to fix it. This includes, "I lost my job", "Teenagers have nothing to do", "My employer doesn't pay me enough". People still expect of and ask for these things despite governments' horrible record.
To name various failures of government:
-The national minimum wage (causing youth unemployment)
-The NHS (massively inefficient)
-World War II (explains itself)
-The illegalisation of drugs (bringing huge revenues to drug dealers)
-The war in Iraq (certainly could have been handled far better)
-Nationalised utilities (inefficient)
-Keynesian economics of the post war era (caused the inflation of the 70s)

That's not to say that the governments who passed these laws didn't start out with good intentions; I'm sure they did. But these policies have been failures; some catastrophic ones, others more minor. I should note here that when I'm talking about the failure of government, I mean the failure of government when it tries to play an active role in society; in fact, most of the 'successes' of government have been when the government has decided to stop managing something! But is it possible to name many successes of government when it tries to play an active role? I suppose general laws like those against stealing and murder have been successful, but even this is impossible to tell since we don't know what the situation would be like if no such laws exist, as they always have existed.

Parties often promise various things which it will achieve when it takes power. Obama will bring healthcare for all. Cameron will bring a more efficient NHS. Are either of these claims realistic? Probably not. It just seems extremely difficult for governments to ever actually achieve anything.

I'm not entirely sure why this is. Companies achieve things all the times, and thank God they do. It could be that since the government is not profit driven, it has no incentive to succeed. But this doesn't seem to be true; parties have a great incentive to succeed in order to remain in power, which is after all what they are looking for. If a government is able to be efficient, surely it will attract votes and thus will be able to keep its job. This doesn't seem to be all too different from how the executive board of a company operates. Perhaps the problem lies in the sheer scale of government; trying to run a whole society just isn't possible, regardless of incentives. But I think the reason could be that voters simply aren't interested in efficiency. Do most voters realise how much of a failure the NHS has been? Probably not. Even if the next party was able to amazingly streamline government to make it ultra-efficient, how many votes would that attract? A few, not many. Votes come from making promises (however ridiculous) and having great PR. Perhaps the incentives of government could be fixed with a very educated public, which would finally lead to efficient government.

Governments are bad at doing things. But, whoever wins the election, the government stays in power.