The history of net metering comes out of the fact that for many years, smart meters for electricity were very expensive, and not widely deployed. As such, net metering was a natural solution to the billing problem. A user who over-produced for their needs would just run the meter backwards during sunny days, and forwards at night, creating a net metering situation.

It's only with Smart Meters that the utilities can accurately measure per-house production and consumption separately. It's certainly possible to create new billing plans that take advantage of the Smart Meters, but with the capital nature of solar investments, there's a lot of legacy installs to deal with, and those people get angry when they deal they signed up for is changed without grandfathering them into the old way.