Cable TV was once the ultimate entertainment necessity. The over-the-air days of VHF/UHF television signals couldn't keep up with voracious viewers who needed more, more, more channels. Having a cable directly pumping all that content into your home became the norm, and the cable providers—which likely provide your high-speed broadband internet access as well—knew they had you on the hook.
Sling TV is the streaming service that also offers live TV over the internet. It’s essentially cable TV without the contract or the massive bill. Currently, if you sign up for Sling TV you get a Free Roku. They also offer a free 7-day trial membership to try out their service. The service works on every major OTT streaming device and recently began offering a cloud DVR. Sling TV also streams NBC live online along with Fox and ABC in select markets.
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.