Think of this way. You have a 1 inch pipe that you need to pour water into to keep the pool full. It works great for a while. Now you build a bigger pool. Bigger pool needs more water. You can't get enough water through the 1 inch pipe to keep the bigger pool full. You need a bigger pipe. Now you put a 5 inch pipe in and your problem is solved.
That's what streaming is. Pushing data, that is audio or audio & video (the "water") to your receiver (the little "pool") or TV (bigger "pool"). Video requires a bigger pipe (more internet bandwidth) because it's a lot more data that needs to get to your entertainment system. Cable internet is a bigger "pipe" than 3g or 4g. But 4g is big enough to reasonably stream video. I hope that helps a little.
We have been hoping to drop cable for a while now, but there are still a few channels and shows we can't get anywhere else yet. Plus I'm finding that the alternatives are not mature enough yet. We subscribe to Netflix, both DVD/BluRay and streaming. At home we would prefer to do all streaming. But at least 2/3 of all TV shows and movies are not available to stream. That's not a failing of Netflix as much as it is a failing of studios and copyright owners to get with the program.
Here's a company to keep an eye on. They are growing, but not fast enough for me. At least they carry the major OTA networks. If they can get some cable channels like USA Network and TNT...