This has a lot to do with how products were marketed at the end of the 19th and start of the 20th century. In the case of oil ("Standard Oil"), for example, the purpose was to be able to communicate the idea that a particular product was standardized and of the same quality no matter if it was purchased in locality A or locality B. During this period many different companies produced kerosene, for example, but the quality of that kerosene could vary dramatically between companies and even between batches coming from one company. So the name "standard" was meant to imply that the product was the same across participating companies (remember, many producers make up the Standard Oil company... which later resulted in some trust busting) and markets.

Source: Daniel Yergin, The Prize: The Epic Quest for Oil, Money and Power.