There are several reasons to doubt that most people will voluntarily decrease their consumption, in spite of the fact that decreasing consumption is typically simpler, if not necessarily easier, than increasing income (unless they are already consuming the bare minimum needed for survival). Perhaps the best of these reasons is the simple fact that consumption continues to rise. No one is forcing people to buy new things (though it could be argue that corporations have become very good at psychological manipulation to that end).
Decreasing consumption tends to go against one of our most basic drives, to mold our environment for maximum comfort and pleasure. People are attracted to artificial environments such as cities and suburbs, which require a high level of consumption (waste) to be maintained, effectively driving up the cost of survival for their residents. As a result, they are more likely to seek ways to increase their income than (voluntarily) cut back on what they use up.
For those who consume a considerable amount of information and crave understanding, the educational prerequisite for voluntary reduction in consumption may be acquired by accident. They may, however, be confident enough in their ability to innovate (increase the ease of consumption) that they will not accept any limitations. On the other hand, people who are more interested in things than ideas are more inclined to learn mostly by experience, and may take too long to become convinced of the need to reduce consumption.
Then there is research showing that consumption has many of the characteristics of addiction. The more we have, the more we want, and we become progressively less conscious of why. The addiction interferes with our functioning (taking over our lives, not to mention destroying the environment), and each day it is more difficult to stop.
Despite these reasons, there is a growing number of people at least attempting to cut back, embracing the so-called “lifestyles of health and sustainability.” Their motivations range from spiritual to physical, including: love and respect for Nature (held by many environmentalists); a reaction to the stress of “keeping up with the Joneses”; and (in my case) fear of being responsible for mass pain and death, as well as the elimination of a decent future for everyone and everything else.