Uhh..not always. The work is balanced out, but often, there is a net loss of jobs. There may always be a need for mundane labor, but that doesn't mean it will be priced at a point that makes living very sustainable. And no, technology doesn't necessarily make sustenance cheaper -- perhaps in theory but not in practice. Technology, like any other kind of a driver of industrial development, frequently concentrates power in the hands of those who can take it. Sometimes, that happens in a way that does make it such that more people can live better on less. It also sometimes happens in a way that blots out much of China's skyline with dangerous smog.

The ability for people to be able to live well, on the whole, is something that depends on society. Technology is merely a lever, not an autonomous agent or operator.

Technology doesn't inherently reduce the number of quality jobs, but in very recent history it appears to have had this effect. From the MIT Technology Review:

http://www.technologyreview.com/review/426436/tectonic-shift...

Obviously, when 7 billion people are involved (or whatever the current population of the planet) the dynamics of this are complex and take time to play out. My point was countering the "jobs lost!" hysteria with "jobs get created, tends to balance out." Pardon the lack of encyclopedic thoroughness in a 3-line post in casual discussion.

There is no reason to think that the number jobs gained by new technology are equal to the number of jobs lost. In fact, based on the fact that we currently have a 40 hour standard work weak, it seems like the average time spent working per person has decreased. Over a long period of time, I suspect this is the number that will adjust to maintain employment.