Most people don't need a gigabit per second to their home, but it's a chicken-and-egg problem. ISPs won't provide that kind of speed because no applications take advantage of it, and applications don't take advantage of it because no ISP provides that kind of speed. At some point, somebody has to break that paradox on one side of that, and it makes more sense for the ISP to do so.
If you release an application that only works well on a very fast connection (say, it needs hundreds of megabits), nobody will use it at all, because nobody can. But if you as an ISP provide people with more speed than they need (like a gigabit), people can still use that connection, even if it's more than they need.
There are lots of things that you can do on a very fast connection (like a gigabit per second) that aren't practical or possible on a slower connection (like 5 or 10 or 20 megabits per second). Some of these we could think of right now, but other things somebody might not have even thought of yet. There are also classes of service that work better on a faster connection.
For example, imagine a virtual external hard disk. Right now, while there are services like dropbox or skydrive, you don't typically use these like an external hard disk; you wouldn't put things on it and run them entirely over the network. But if you've got a gigabit connection, and low latency to the server, that's fast enough to treat such a service as a network disk instead of a download service. That is to say that you can leave the data entirely on the remote server and access it read-by-read over the internet. Suddenly, you could provide a virtual hard disk service that would have a pretty different experience from dropbox (which stores everything locally and syncs to the server).
Another might be really low latency video streaming. Think something like OnLive, but with much lower latency and much higher quality, to the extent where you couldn't tell the difference between a game running on your local computer and a game running in the cloud. That's an example of something that works today, but could work much much better if we had really fast connections.
I'm sure there are many more kinds of things that people haven't invented or discovered yet that would also be enabled by very fast connectivity, but if I knew what they were, I'd be rich --
Developer: Tomato/MLPPP, Linux/MLPPP, etc »fixppp.org