I don't think there was a time Cable didn't have ads, certain channels like HBO yeah, but never cable as a whole. The attraction was just having way more content.

In the 1950s when Cable started in the US, there were no Cable channels. Cable was literally renting a pipe to a big antenna instead of your own small antenna in your house, so you got broadcast with better signal strength.

The first Cable channel was HBO. The second was TBS, it had ads from the beginning.