Here's a nice analogy, drawn from the recently widened and renovated A2 highway, running all the way from Amsterdam to Maastricht and beyond. After a heist of a Brink's money storage facility near Amsterdam, the robbers were able to escape to Eindhoven and subsequently disappear altogher. According to media reports, they had been doing 240 km/hr on the A2.
We may not need to speed that much all the time, but sometimes it's nice. And that's why we need gigabit networks!