What are politicians for?

What is the function of politicians? I ask because the coalition is making pitifully slow progress in reforming the provision of social care.
The thing is, this is the sort of straightforwardish job that government should do. We have a ready-made solution to a genuine problem. But it seems the Dilnot report is being as ignored as the Mirrlees review, which vindicates of Alan Blinder's saying that "economists have the least influence on policy where they know the most and are most agreed."
We see here two features of this government. One is a failure to be guided by good advice. The other is an inability to perform a core function of the state - to rectify a market failure. And this is all the social care problem is; there's a missing market in insurance against the small danger of incurring a large expense.
And here's my problem. There are two classes of issues:
1. Those that governments, in principle, can address by being able to marshall collective action and informed opinion, but are not addressing: these include reform of social care and the tax system, for example.
2. Those problems that are irremediable. I'd put increasing long-term GDP growth and eliminating troubled families in this class.
My question is: what issues fall outside of these two classes? Which are in the set of problems that governments can solve (or ameliorate) and is solving?
The Lib Dems think the answer includes reform of the House of Lords. But only a minority of cranks think this is an important issue.
Put this another way: how many social or economic problems of, say, the last 20 years have been solved by politicians, as distinct from by the passage of time or by economic growth?
My problem here is not a UK one. Indeed, the two biggest current obstacles to western economic growth are both the result of politicians' failure: the US "fiscal cliff" and the failure to resolve or patch up the euro area crisis.
Now, one might argue that I'm looking too much through a technocratic prism. Perhaps it's the function of politicians to embody particular values.
There might have been a time when this was true - when, for example, Tories favoured negative liberty and Labour equality. But such conflicts of values are rare now. And even were they not, in a Macintyrean world, few people are capable of making coherent arguments about values. Politicians have a base in neither expertise nor moral authority.
Now, I am not arguing here for a "strong man" dictator. All I'm doing is posing the question: what are politicians for? Unless they can answer this - and they show little appetite for doing so - then mainstream politics will look like no more than a circlejerk.