Discussion: How on earth do home fibre modems handle all that throughput?

I have been busting my head for a while now:

You have a 1G fibre broadband, which comes with the ISP router. That router supports:

• NAT
• SPI
• Some port forwarding
• Wireless
• A Web GUI
• Basic DoS protection

And it is supposed to do 1G of bandwidth. I mean how? Enterprise equipment requires at least a full U appliance to do 1G of NATted throughput. What am I missing here?