100% of the time ? not going to happen
So let's say I'm an ISP and I bring a fiber to your home, and gives you a gigabit ethernet port. You cannot expect all current and future customers to be able to use 1 Gbit/s at the same time. You would need a big non blocking switch with as many ports as subscribers, the technology for this does not exist once you reach a large customer base.
Now do you want me to shape your link to 0.1Mbit/s, because that's the only thing I can guarantee if all customers uses their link at the same time ? Or you'd rather have the 1Gbit/s possible bandwidth ?
Which one is better:
1) guaranteed 0.1Mbit/s for 10$, 5Mbit/s for 100$, 1Gbit/s for 4000$ 2) possible 1Gbit/s for 20$ ?
If you take the globalized approach, you cannot have business like Netflix, they destabilize the equation.