Backbone capacity ISP

I am just trying to learn a bit more about networking, especially backbone networks for ISPs.

So in my country I know that the maximum capacity in the backbone of at least one ISP is 800Gs. However, I really have a hard time grasping how that is enough. I mean, I know that depending on where the signal goes from and to it doesn't necessarily needs to go through the entire backbone and take up capacity. But still, many 1G connections are available for e.g. regular consumers, and more for companies etc. And in my mind I find it kind of insane that with the amount of available 1G connections, that there isn't e.g. 800 users using the max bandwidth of their fiber or coax connections, which has to go through the backbone in order to get outside the country etc.

What am I missing here ?