I somewhat recently learned about the propaganda from the FBI in the 60's and 70's to discourage hitchhiking. (possibly a covert assault on civil rights protesters hitching to rallies) It's easy to be scared of failure, suffering or what can go wrong... but not everyone is excited about what could go right.

Ultimately, I believe a big reason why hitchhiking is not very prevalent is that both the cost of air travel and vehicle ownership has gone down significantly over time. (adjusted for inflation)