Executives couldn't agree on how long to make old episodes available for subscribers. Some gave viewers only a day to catch up on a show they missed because the broadcasters had sold the reruns to another service. Others made past series available to subscribers for a month. Consumers became confused about where to go and how long they had to binge-watch a show. Some TV networks were slow to make their channels available online.
Internet providers are not available in all areas. Internet service and speeds vary by zip code and even street. Cable TV service may be available in some areas, but not in others. The easiest way to see service for your address and what internet you can get is to enter your zip and then call, but the above shows major TV and internet providers and their major service operation areas.
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.