Many of the passengers apparently are members of the working class rather than the affluent segment of the population. Spanish is commonly spoken on the buses. Speaking of bicycles, there are lanes for them everywhere and those lanes are heavily used. Boulder's mayor rides a bike to work. So do lawyers and downtown merchants.
Students do too, of course.
Still, Boulder has more cars than licensed drivers. Those cars are, by and large, nice ones. There are quite a few people in Boulder who not only own several modes of transportation but several expensive homes in far-flung places. They live here from time to time, particularly during ski season. State law does not require that motorcyclists don protective gear.