There are quite a few Wall Street deal makers who, several times a year, make the trek to Washington, where they find ways to inject their ideas into the public policy discourse. Steve Mnuchin is not one of them. Mr. Mnuchin, Donald J. Trump’s nominee to be Treasury secretary, doesn’t serve on the boards of any policy-oriented institutions, and there is no evidence he has ever appeared on a panel at the Brookings Institution, the American Enterprise Institute or any of the other places in Washington where people debate economic policy. “I had never heard of him,” said Stan Veuger, an economic policy expert at A.E.I., an often-heard comment from Washington policy people since Mr. Mnuchin emerged as a candidate to run the Treasury Department. There’s nothing wrong with that, of course, and speaking on panels at the Brookings Institution is neither a prerequisite for high government office nor a guarantee that a person will be any good at it. Mr. Mnuchin is, from the accounts of those who have worked with him, smart, capable and pragmatic. But his appointment is part of a recurring theme as Mr. Trump has assembled his cabinet. Most of his appointees have little in the way of directly relevant policy experience. Mr. Trump, who has never worked in government at any level, has also named a chief of staff (Reince Priebus) and chief White House strategist (Stephen K. Bannon) of whom the same can be said. In a more normal administration, a person like Mr. Mnuchin would be lined up for a cushy ambassadorship in a pleasant city like Paris or London instead of serving as the nation’s chief economic statesman. There are exceptions to this, with nominations of conventionally qualified candidates like Representative Tom Price to lead health and human services and the former labor secretary Elaine Chao to run the Transportation Department. But with his appointments so far — to the list add the commerce secretary nominee Wilbur Ross and the education secretary nominee Betsy DeVos — Mr. Trump seems to be betting that nuts-and-bolts experience running government agencies and wrestling with the hard technical details of public policy just don’t matter.