It's done like that to try and approximately apportion the cost based on each user's use of the infrastructure. The cost is almost entirely driven by peak use

It's done like that to try and approximately apportion the cost based on each user's use of the infrastructure. The cost is almost entirely driven by peak use though, so what would actually be "fairer" (or at least more cost-reflective) is to charge the transmission cost based on your individual contribution to peak demand on the infrastructure. People kind of hate that though because it's difficult for most consumers to predict or control their contribution to peak demand, and for the same reason it doesn't drive behaviour change / more efficient use of the infrastructure as much as you'd like. In the end it'd probably still be about 60% of your bill anyway.