Because efficient companies produce goods and services for lower prices than inefficient companies, which, happening at scale throughout the economy, lowers the cost of living and raises the standard of living for everyone. An increase in the amount of goods and services produced per head is the definition of economic growth, which most of us consider to be a good thing. Improvements to our quality of living essentially require economic growth.

Take a listen to this NPR Planet Money podcast (and article) called "The History of Light" [1]. It describes how much it cost to light a room, in terms of a typical day's wages, at various points in history until today:

> The history of light is the history of economic growth — of things getting faster, cheaper, and more efficient. In Babylonian times, 4,000 years ago, a day's labor would buy very little light. You could buy enough light to illuminate a room but not for very long. Maybe 10 minutes. It was really expensive.

Today, a day's worth of wages can afford to light a room for thousands of hours. This affordability has radically changed our society, mostly for the positive. It's now possible to study and be productive in the evening. Many of the improvements to the efficiency of lighting also enabled cheap heating as well.

Another related interesting article is "The $3500 Shirt - A History Lesson in Economics" [2]. This one traces the cost of clothing from the middle ages to today. Consider: why did people used to wear clothing until it became rags? Because clothing was extraordinarily labor-intensive and thus expensive. A single shirt back then might cost $3500 in today's money. Now clothing is a negligible cost for most people in the USA, including the poor.

Companies (and individuals) and their desire for efficient production have brought these costs down, and the costs of so many other goods. I've heard it said that today the average person in America has a quality of living substantially better than that of a medieval king. I believe it: with our lighting, heating, and potable water delivered to our homes; sanitary food & restrooms; medical and dental care, etc. -- all available to (mostly) everyone due to low prices. Not to mention the luxuries available to us in our homes like television, music, radio, video games, etc. Cheap spices from everywhere in the world. Food from most everywhere is available at low prices and high quality in local supermarkets. Travel is cheap, and many people can afford to travel virtually anywhere urban in the world within 24 to 48 hours by aircraft - amazing by any historical standard. And it's so reliable we take it for granted.

All changes that originate from economic growth.

During the industrial revolution, a lot of automation replaced human labor in clothing production. This did have the negative effect of putting the spinsters and weavers and so on out of business, but had the positive effect of making clothing vastly cheaper for everyone. People found new jobs and society continued, and was better off overall. Similarly, the development of the automobile largely put the industry supporting the horse-and-buggy out of business. But everyone was better off overall having fast and cheap transportation.

So how do we know that it's true? I suppose we don't have any way of saying in a particular case, but we can look to history to see how innovations that made products and services cheaper have benefited society overall.

Perhaps 1000 years in the future, they will trace how much computing a day's wages could buy, and how that went on to transform society too.

[1] http://www.npr.org/2014/05/02/309040279/in-4-000-years-one-t...

[2] http://www.sleuthsayers.org/2013/06/the-3500-shirt-history-l... - also discussed on HN [3]

[3] https://news.ycombinator.com/item?id=8940950