There is another reason the seventies lose their identity, and it is because generational demarcations ended. If you look at recent generations: Gen. X (1965-1979), Millennial (1980-1994) and Gen. Z (1995-2009), the dividing points are quite artificial, based on the notion that a cultural generation should be 15 years, half of a family generation, 30 years. We can not say a child born in 1962 was exposed to a different environment from one born in 1966, even though a sudden drop in the birth rate ends the designated Baby Boom after 1964. Same with 1992 and 1996. In contrast, a child born in 1952 had very different concerns versus one born four years later. A man born in 1952 could be drafted, against his will, if his lottery number came up first, and there were no more 4-year undergraduate deferrals to keep him from being drafted in 1972, in the middle of his sophomore year in college. In contrast, one born in 1956 moved to adulthood as if the draft never happened. For this reason, I place the end of the cultural sixties at July 1, 1973, the day selective service ended.
Two older generations had significant changes within. The Silent Generation (1927-1945) starts with Korean War veterans (much in common with those of WWII) and ends with Vietnam vets, treated very differently and are among those who ushered in the counterculture. The Baby Boom (1946-1964) starts with Vietnam vets and ends differently. In contrast, the differences among those born after 1960 occur slowly without prominent demarcation points. The people slowly assimilate new technology, new electronics and new standards. While technology is a point of distinction for every generation, it moves to the forefront in more recent generations.
In fact, we can step back some 45 years to 1973 and see a time when many order of life issues are still much like those of today: cars, highways, airplanes, hotels, shopping centers, classic rock music, dress codes (or lack thereof). If you step a mere 15 years farther (1958), you are in an era of Jim Crow segregation, passenger railroads, different dress codes, and recorded music that is much less developed.