The 1970s are called the "Me Decade" as a way of contrasting them from the 1960s. In the 1960s, Americans were involved in many different kinds of political and cultural movements. It was, of course, the decade of the Civil Rights Movement and the movement for women's rights. It was the decade of protests against the Vietnam War. People in that generation were interested in trying to (they thought) improve the whole nation or the whole society.
By contrast, people in the 1970s pulled back from politics. This is sort of like what happened in the "return to normalcy" of the 1920s. People were tired of being involved in big issues. They wanted to pull back and take care of themselves instead. During this decade, people turned away from large protest movements and focused on themselves. They turned to things like psychotherapy and religious gurus who were supposed to fix what was wrong with them as individuals.
Overall, then, the '70s are seen as a decade in which people stopped being interested in fixing the whole society and started to think only of fixing themselves. Therefore, it has been called the "Me Decade."
During the 1960s, the United States was still recovering from World War II. The ideas of this war were still fresh in people's minds, and with the Cold War in full swing, people were interested in improving their country and society as a whole. Sometimes this is referred to as "communitarianism"--the idea that the community is more important than the individual. In 1961, President Kennedy famously said, "ask not what your country can do for you, but what you can do for your country". This quote underscores the ideals of the 1960s.
However, during the 1970s as things began to wind down and feel more peaceful, people became more interested in bettering themselves. Individualism became more important as people became dissatisfied with wars and politics. They realized that these things could not fix society, and some reasoned that perhaps nurturing the individual would do a better job. As a result, fashion completely changed. Rules were broken; women continued to assert themselves socially; expressions of one's own self were encouraged. Some people took this as far as "streaking", or running naked, while others took part in the less-startling fads such as "pet rocks" or horrific color combinations of clothing. Since the 1970s were all about expressing oneself, they were dubbed the "Me Decade".
The term "Me Decade" was coined by Tom Wolfe to describe the decade of the 1970s.
The 1970s were a time when people were tired of political and social issues. The decade was marked by the emergence of the lower-middle class and by economic prosperity. People were becoming increasingly individualistic (rather than communitarian). The people had already witnessed the civil rights movements and Vietnam war in the preceding decade, and were becoming disinterested in governmental policies and debates. This was a time of self-discovery and newly manifested individualism, including drugs, spiritual gurus and music. This was also a time when some of the current technology titans started their ventures, instead of working for someone else, another trait of "Me decade". Such entrepreneurs includes Steve Jobs and Bill Gates.
Thus, a time of self-realization and self-improvement was aptly termed as the "me decade."