That's an interesting perspective. I mean, today, it seems impossible to imagine any use case for > 100Mb/s. After all, it can stream 4k HD video!

But I think the very way we use computers is restricted by what is possible on commodity infrastructure. The fact that 100Mb/s is overkill for many customers is simply because the average speed is much lower, so nobody has bothered to develop applications that make use of that additional bandwidth. If 100Mb/s became something everyone had, I'm sure we would start to see applications that require such speeds to be useable. I don't know what those applications would be, but I'm sure they would come to exist.

A 56k modem is overkill if you're browsing a text-only internet, but it would be pretty hard to use the internet of today with one :).