There are some great responses above. Thank you all!

I've been playing with some ideas from James Neill, a professor at the University of Canberra. He talks about two kinds of risk: R- and R+. R-, or negative risk, is whatever strategies we use to minimize risk of loss to maintain status quo. For example, (if I understand him) we might wear helmets to minimize the chance of cracking our noggins. On the other hand, R+ is risk for gain -- when we engage in a risk for growth or gain. Choosing to bike on the road, as some have mentioned, offers a significant positive experience that outweighs (in our minds) the risk of being doored or sideswiped or whatever.

R- philosophy is "risk aversity", e.g. insurance, law, etc.

R+ philosophy is "risk engagement" e.. exploration, sport, etc.

He talks about Outward Bound programs as opportunities to embrace the value of risk as a means of education and self-discovery. Sounds a lot like some of our reasons to cycle, no?

He discusses risk education as well: R- is education about how to manage negative risks (e.g. safe sex class) , and R+ is education about how to manage positive risks (kama sutra workshop).

The goal of R- is to avoid negative consequences, and the goal of R+ is to obtain positive consequences.
Obviously, in cycling we all probably have a combination of risk strategies, from avoiding falling and cracking our heads open, to experiencing the thrill of speed, riding down mountains, etc.

He also believes, as do I, that society has swung the pendulum towards risk aversity and away from risk embracing. Look how we treat our kids nowadays in terms of "keeping them safe."

Anyway, I find the topic fascinating. . .