Agree with you that the market isn't able to pick out value, especially value that isn't easily exchangeable for money. Social work is of indispensable value from a particular perspective, and social workers are in short supply in many countries including my own (Singapore).

However the market does not exist by itself, it exists in a structure put in place by governments, with many other players such as non-profits, interest groups, etc. At this point in time, social workers, teachers, etc. have to be supported by funding from governments and donors.

Short of having a more enlightened economic system, what we can hope for right now is for governments to better reward professions that provide such value.