> The reality is that cable was a paid premium service, unlike broadcast TV, which was free and littered with ads.

The reality is, most cable channels had ads from day one. Less ads than most broadcast stations (which made up most of the channels you had on cable at the start anyways) but still a lot of the first cable-only channels had ads from the start. WTBS had ads on cable in 1976. MSG/USA had ads on cable starting in 1977. CNN had ads on day one in 1980. MTV had ads on day one in 1981.