Realtime electricity changes

Why doesn't the electric company support billing me at a rate that can change often each day(hourly?) instead of quarterly?

This would work by them sending a signal with the current rate over the power line and each house would have a box (by the thermostat?) that shows the current rate.  That info could also be sent to any automatic electric appliances (heater, water heater, air conditioner, etc) so that they would automatically adjust to the current rate.  The heater thermostat temp would decrease as the rate increases and vice versa.  Then I could also quickly check the current rate if I need to run a high usage appliance (arc welder, or even possibly microwave).

Right now the only way they can affect usage is by cycling or turning off certain appliances but that is like having a car with only a go and stop button instead of a brake and accelerator pedal.

Realtime market pricing would give people the info needed to use the correct amount of electricity. This would greatly reduce the need for using expensive methods for generating electricity (that are probably also less energy efficient).