Large businesses, governments, scientists with large concrete tubes under the Swiss countryside, and provider trunk links.
Absolutely no use for home individuals. I've used a symmetric 1Gb connection into my laptop fed off a 10Gb switch.... I can tell you that you soon find you can't do anything about speeding up transatlantic data, you can't do anything about servers you're trying to access having insufficient capacity (or rate-limiting you), you don't need that much bandwidth for streaming.....
Basically, for most people a proper 10 or 20Mb, even asymmetric service would be more than enough as long as its not the heavily contended rate-limited packet-shaped rubbish stuff you get now. But for that, people would have to agree to pay more and the providers would have to stop this stupid race to the bottom on pricing.
Quality not quantity I say (service, not headline speeds)