That varied by region. When cable came to my town in the early 1980s, HBO and Cinemax were part of the local cable provider's basic package. That lasted until the next provider bought them out.

Oh, sure, definitely some providers did some things like that early on to drive growth, especially when they were trying to drive into the areas less dissatisfied with existing broadcast quality then the initial cable markets. (And even once it stopped, it was common to bundle premium channels into the basic cost for a limited time for new customer acquisition.)