I Remember Hitchhiking

Freakonomics explores a couple reasons for the decline in hitchhiking: fear and the rise of women drivers and an associated rise in car ownership and multi-car families.  I'd add a couple: the rise of limited access highways and the diversion of traffic to them--even if hitchhiking is not explicitly prohibited it's harder to stop and pick up person in the midst of 70 mph traffic; the tipping point phenomena--if it's not often done it feels riskier.

I used to hitchhike on my way home from cross-country practice, though mostly I ended up walking all the way.  Modern kids are spoiled.