My sister bought a Raleigh Super Course in 1973. I think the main driver of the bike boom was technological, in that bikes that would get you somewhere in a reasonable length of time were now available. Before that, the only adult bikes any of us had seen were the 3 speed English utility bikes that inexplicably were called "English Racers".
I didn't see any racing or anyone being particularly elitist. People just rode to ride, or to get somewhere. Hardly anyone had bike specific clothing. It wasn't like now where you see very average riders kitted up like they were pro team members.