But cable providers didn't factor in that the internet they provide would become their worst enemy via access to streaming video. Services like Netflix, Hulu, and Amazon Video are the most well-known names in what's become known as "cord cutting"—doing away with pay TV and using over-the-air (like the old days) or internet-based services to get all your "television" programming. That means no more paying a huge monthly fee for thousands of hours of TV you don't watch (in theory). Instead, you pay individual services for a la carte programming. It's a lot like paying for just what you watch. Almost.
Although early (VHF) television receivers could receive 12 channels (2-13), the maximum number of channels that could be broadcast in one city was 7: channels 2, 4, either 5 or 6, 7, 9, 11 and 13, as receivers at the time were unable to receive strong (local) signals on adjacent channels without distortion. (There were frequency gaps between 4 and 5, and between 6 and 7, which allowed both to be used in the same city).
The question of "when does it make sense?" can easily be rephrased as "how much money can I save?" and one of the biggest factors will be the price difference between combined internet and TV service or just internet. These are also the options that vary the most widely based on where you live, and the availability of promotions or contracts that can keep prices down for a short time.