The era saw a president (Richard Nixon) removed from office. For a time it appeared that the central authority itself was breaking down. The black, women's, Hispanic, and gay/lesbian movements were in full swing. It seemed that anything was possible, especially in the realms of sex and personal expression. Gay men were the "shock troops of the sexual revolution."
To be sure, a number of books have appeared to characterize the seventies. To me, though, it is all best encapsulated by an essay by Charley Shively called "C@cksucking as an Act of Revolution." In today's advanced industrial world, the idea of an act of revolution seems a quaint fantasy. But it is the conjunction that is so absurd and self-serving. The writer was a c@cksucker and would-be revolutionary. But what necessity links the two? I am reminded of a slogan affected by lesbians during the period: "A woman needs a man like a fish needs a bicycle."
From what I can gather (my experience is not THAT extensive in this realm) fellatio is more commonly a capitalist act, since money often passes from one hand to another. As I say, though, times change.