When did service first start being used to mean "commercially valuable act"?
Was there a specific point at which service started being used regularly as the commercial counterpart to a physical product, i.e. "goods and services"?
From what I've read, service became a popular word in business in the US in the 1920s. Online Etymology Dictionary reports that:
Service industry (as distinct from production) attested from 1938.
I can't find any other more definitive source on the use of the word service in this manner, and it's fairly similar to the expected use of the word service, which makes it even harder to tell.
Solution 1:
The collocation goods and services is centuries old.
The earliest newspaper example of goods and services I could find is the following from 1804 ("From the Vermont Journal. Letters on Banks. Letter V." Political Observatory, vol. I, no. 10, 21 Jan. 1804, p. 1. Readex: America's Historical Newspapers):
It has been believed b some, that the poorer class of people in the neighboring towns, such as have indeed small farms, moderately stocked, but are not only not in the habit of handling much money, but are in debt, to merchants, doctors and tradesmen, for goods and services already received.
The collocation has 22 results in the slightly-earlier Eighteenth Century Collections Online, including this example from 1747 referring to economic transactions (The Case of His Majesty's province of the Massachusetts Bay in New-England, with respect to the expences they were at in taking and securing Cape Breton. S.n, [1747]. Eighteenth Century Collections Online):
And as the Inhabitants of the Province, in their politic Capacity, gave their Bills of Credit, private Persons, Inhabitants of the Province, received them in Exchange for their Goods and Services
And Early English Books Online (covering ~1473-1700) yields 4 more results, including this from 1636 (Jean Desmarets de Saint-Sorlin, Ariana, London, 1636. EEBO.):
The next day she arose before them, and went to make acquaintance with all of that obscure house; then having understood there were some Romans come, that desir'd to speake with the two friends, she went to them to know what their desires were. They signified to her, they were come to offer them their goods and services.
So the dichotomy of gods and services was embedded in language for centuries. The service industry meanwhile began to emerge in the late 19th and early 20th centuries. Early newspaper uses refer to public services like water and electricity ("Denver's Mayor Chosen. Elected President Of The League Of American Municipalities. The Discussion Of City." New York Tribune, 22 Sept. 1899, p. 3. Readex: America's Historical Newspapers.):
When power is granted to a municipality to become the owner and operator of a public service industry, it is always granted without limitation as to time.
That notion builds in the first couple of decades with collocations like "motor car service industry" used to refer to a general field of work ("Speaking the Public Mind Urges Quick on Prohibition." Kansas City Star, Main Edition ed., vol. 81, no. 189, 8 Aug. 1918, p. 4. Readex: America's Historical Newspapers.):
But the tire service stations, that branch of the motor car service industry that is possibly of more convenience to the motorists, are closing at 6 o'clock and remaining closed Sundays and holidays.
As your original source notes, this usage for particular service industries would be supplanted by the language of Depression-era economists, who would distinguish the production and service economies (Bratt, Elmer C. “Did Productivity Increase in the Twenties?” Journal of the American Statistical Association, vol. 34, no. 206, 1939, pp. 326–332. JSTOR.). First, putting industries in plural signals that a broader kind of service is being discussed.
The problem centers around productivity in the service industries, for which no measurements are available.
Then, a few pages later, the author directly contrasts basic industry (involving manufacturing) with service industry.
A larger proportion of the income appears to be saved or paid out to owners in basic industry than in service industry.
Thus a longstanding concept of service was adopted by economists into a sector of the economy.
Solution 2:
In OED, the first citation is from 1936 for this sense of services.
Discovery Nov. 355/2 The distinction between capital goods and current goods is, of course, one of the most important in the whole of economics, but the remarkable growth in the number of those engaged in ‘services’, now estimated at 40 per cent. of the working population, is not so generally realised.
OED definition:
pl. Econ. The section of the economy that supplies needs of the consumer but produces no tangible goods.
For the earlier related senses:
OED's first citation is from 1853 for this sense:
Provision (of labour, material appliances, etc.) for the carrying out of some work for which there is a constant public demand.
OED's first citation is from 1919 for this sense:
Expert advice or assistance given by manufacturers and dealers to secure satisfactory results from goods made or supplied by them; spec., the provision of maintenance or repair work to ensure the efficient running of a motor vehicle, etc.; a routine operation of examination and maintenance performed on a motor vehicle, etc.