Wikipedia's article states the model originated before modern transportation and electricity, when geography forced local consumption, and separately that it became immensely popular during the late-1990s dot-com bubble as a labeled online-retail strategy. These are two different eras for two different senses of the term, and no single year can honestly represent the model's origin.
What would resolve this A source naming a specific first documented instance of direct-to-consumer selling as a deliberate strategy, or one confirming that the modern labeled sense of the term begins specifically with the 1990s wave this research found, with named firms and a year.
OpenWikipedia, Direct-to-Consumer