Earlier quoted context omitted.
"There’s a lot of questions one could ask here, starting with, what does it say about our society that it seems to generate an extremely limited demand for talented poet-musicians, but an apparently infinite demand for specialists in corporate law? (Answer: if 1% of the population controls most of the disposable wealth, what we call “the market” reflects what they think is useful or important, not anybody else.)"
Isn't it interesting that the one example Graeber comes up with is possibly the profession writ large whose demand is largely influenced by a social structure outside of the free-market? Likewise, a over promulgation of workers in finance is suggestive that maybe there is some non-free-market force is incentivising individuals to go into that field...
Non-market interactions are invisible to conventional economics because they're not priced, but they're by no means insignificant. They range from developing-world peasants farming land to which they simply have no title deeds, through to the form of communist praxis which is the dominant social structure of the supposedly free-market west -- the nuclear family. (Or do you present your kids with a bill for their personal care and feeding? Non-dysfunctional families run along lines Marx described as, "to each according to their needs, from each according to their abilities": sharing without reference to individual wealth is explicit in state-recognized marriage vows. That the power/money relationship often reverses a generation later, as adult children support or nurse their aged parents through their last year, just underlines the pattern.)
Graeber, as an anthropologist, is interested in all human interactions, not just marketized ones. And his particular field has been the intersection of the market sector with the non-marketized greater cloud of human relationships.