According to the wiki article that you linked:

However, due to many legal, regulatory and technological obstacles, cable television in the United States in its first 24 years was used almost exclusively to relay terrestrial commercial television stations to remote and inaccessible areas. It also became popular in other areas in which mountainous terrain caused poor reception over the air. Original programming over cable came in 1972 with deregulation of the industry.[1]

So basically for that first 24 years - around '1948 -'72 it was primarily used to get broadcast television to people in areas with poor reception.

Then came cable companies, producing content.. without as many commercials as OTA t.v. I wasn't born early enough to know the 70's, but did grow up with antenna television and remember being introduced to cable. First thing I noticed was that there weren't any ads at all on some channels. When I was a kid the ad free channels on my setup were 09, 10, 19, 20, 21, and some others I'm likely forgetting. I didn't actually have too many more than that, and a lot of that was filler. The ad free channels were the meat and potatoes of my experience!

So, maybe history doesn't say it was marketed that way, maybe the cable companies didn't either, I won't claim to know, but I will tell you that seeing channels without ads was a pitch on its own back then, you noticed it when you visited others homes and talked about it, others noticed when they visited out home and thought about getting it themselves etc.

Maybe it wasn't a pitch, and the whole deal, but it was damned sure a selling point.

We got reception just fine, somehow even in my rural area, what we didn't get was relatively new, commercial free movies, or titties.