• the network is a natural monopoly - i.e. it makes no sense to have separate networks in competition. So the one network needs to be regulated if you want it to be open to all comers on equal terms. This is not as simple as it sounds:

• the one fundamental technical feature of power is that it is almost impossible to store, thus making it imperative that supply balances demand at all times. That means that the network operator has to have to ability to bring or to take out production capacity online at very short notice and without the relevant producers having much of a say in the matter;

• the one fundamental political feature of power is that lack of supply is, quite simply, not tolerable in our society. It is vitally important for the economy to run and for our lifes to proceed. Thus, again, the requirement for a strong regulator able to impose the availability of spare capacity at all times, and to impose stringent technical constraints on the production of all so that the network is not put at risk.

Then you have the additional elements that investments come in big lumps, and it is thus hard sometimes to finetune capacity - so you end up with excess capacity or looming shortages in alternance. It also means that licensing and permitting procedures, and local hostility can have a big impact on a given project and thus on the overall balance of the market.

And, as I wrote before, some technologies are more sensitive to financing costs than others, so pushing for pure "market" solutions is de facto a technology choice - that of coal and natural gas-fired plants vs wind or nuclear.

In the long run, we're all dead. John Maynard Keynes