Hippies were young adults living back in the 1960s and early 1970s, and buy far the most popular bicycle for young adults in that time period was the ten-speed racer, that is why there are so many old ten-speeds laying around everywhere today. The chopper bikes were what kids rode back then before puberty. Cruisers were for nerds and old people, or people with no money. So given a choice the hippy would go for the ten-speed, but if they were poor they would settle for any old adult-sized used bike they could get their hands on.