In the USA the traditional model of the vertically integrated electric utility with a transmission system designed to serve its own customers worked extremely well for decades. As dependence on a reliable supply of electricity grew and electricity was transported over increasingly greater distances, power pools were formed and interconnections developed. Transactions were relatively few and generally planned well in advance.
However, in the last decade of the 20th century, some US policy makers and academics projected that the electrical power industry would ultimately experience deregulation and independent system operators (ISOs) and regional transmission organizations (RTOs) were established. They were conceived as the way to handle the vastly increased number of transactions that take place in a competitive environment. About a dozen states decided to deregulate but some pulled back following the California electricity crisis of 2000 and 2001.
Short of hanging solar panels on my house, I have never had the opportunity to choose who provides my power. Most of us haven't. To no one's surprise, utilities regularly rank as the most-complained-against companies in the United States; Comcast is one thing but LADWP is a whole 'nuther monster.