Why the 70's? Because it was in the latter half of that decade that industry decided to capitalise on the hipness of being "radical;" when long hair, tie-dyed shirts, peace symbols and other nonconformist forms of apparel went from being political to profitable. So, we ended up with corporate execs and lawyers wearing polyester leisure suits with bell bottom pants and lapels out to the shoulder and either tie-dyed or flower print shirts to show that they were "with it." If a tie was worn it was as wide as a bib. And let us not forget the granny dress and the ultra-short miniskirt in which 99.99999% of women then, as well (oh Lord) as today, should never be seen.
Yes, it was in the 70's that the long precipitous descent of taste in style began. But that was just the beginning; the stage was set for the next great decline: Punk followed by Grunge, from which society never recovered. All anyone has to do is walk around any city, or college/university in a metropolitan area, or public high school and see the remnants of the waste laid by the pop culture of the 80's.
Then when you thought things couldn't get any worse, along came rap and hip-hop with its foul language and glorification of the criminal life. As soon as the "music" became commercially viable so did the corresponding "fashion" of low-rise baggy jeans and oversized clothing. Oh, lets not forget the jock/frat mentality of the middle class with their backwards baseball caps and faux hip-hop clothes and scraggy beards.
My generation has no one to blame but itself. We raised a generation (along with the ensuing generation) of kids who were told that they were all just great, that everyone was special and each and every one was entitled to whatever he or she wanted and instilling some form of discipline would damage their self-esteem. So, our society is blessed with two or more generations of people who can't be told anything, even how to dress. Fresh out of school (either graduating or dropping out) they expect to be paid whatever they want, come to work whenever they want, and work as much or as little as they want because that's how they've been conditioned to think.