I mean, it can’t be that important of a job if the position is constantly being left unfilled for hundreds of days at a time, as it is.
They oversee a lot of different responsibilities…
The basic functions of the Department of the Treasury mainly include:
Producing all currency, coinage and postage stamps of the U.S.;
Collecting taxes, duties and money paid to and due to the U.S.:
Paying all bills of the U.S.;
Managing the federal finances;
Managing government accounts and the United States public debt;
Supervising national banks and thrift institutions;
Advising on domestic and international financial, monetary, economic, trade and tax policy (fiscal policy being the sum of these);
Enforcing federal finance and tax laws;
Investigating and prosecuting tax evaders;
Publishing statistical reports.
I wouldn’t characterize any of them as unimportant.
I think dolphinboy is thinking of the Secretary of the Treasury. The Treasurer looks like a position that could be eliminated with no downside, except for the current holder of the office.
The Treasurer is largely a sinecure position at this point. Basically their main duty consists of advising the Secretary of the Treasury on various issues and coming up with a nice signature to put on currency.
Doesn’t he spend all his time signing currency notes?
She. Since 1949, the position has always been filled by a woman.
My bad. The position of Treasurer is mostly a pointless position. I’m not sure why the Secretary of the Treasury isn’t worthy of signing bank notes.
Yeah, but it’s way easier than it used to be. Since 1987 he uses a waldo attached to a frame with 32 pens so he can sign a whole sheet at once before it goes to the cutting machine. 
Ah, that’s where waldo is.
What does the Treasurer do on a day-to-day basis? For example, does the Treasurer generally work a typical 9-5 day with an overflowing inbox of tasks to do, or is it one of those positions that is more like “we’ll call you if we need you” and they come in once every few months for a photo-shoot or to provide a ceremonial “approval” of something that’s already been decided by the people who do the real work?
I get that the Treasurer is expected to “advise” other officials on various matters, but does this mean that they are writing research reports all day or is the “advice” more like a wink and a nod and a phone call once in a while? Like, if I rode the DC Metro enough, would I expect to see a harried Rosa Gumataotao Rios running around trying to make all her meetings while being berated by her supervisor for not using the correct cover sheets on her weekly TPS Currency Advisory Reports?
The banknotes are signed by both the Secretary of the Treasury and the Treasurer.
Does overseeing the Secret Service work its way in there?
Not since March 1, 2003 when the SS was transferred from the Treasury Department to the Department of Homeland Security.
The Secret Service hasn’t been part of the U.S. Department Under of the Treasury since 2003. It now falls under the U.S. Department of Homeland Security.
And even when it was under Treasury, it was the Secretary’s job to oversee it. The Treasurer of the United States isn’t even subject to Senate confirmation. Congress isn’t going to put a major law enforcement agency under such an office.
According to Treasury.gov:
The office of Treasurer of the United States is the only Treasury office older than the Department itself. The Treasurer was originally charged with the receipt and custody of government funds, though many of these functions have been taken over by different Treasury Bureaus. Responsibility for oversight of the Bureau of Engraving and Printing (BEP) and the United States Mint was assigned to the Treasurer in 1981. In 1994, the Treasurer was named National Honorary Director of the U.S. Savings Bonds Campaign.
So, basically, “upper management.”