I have fond memories of hitchhiking from Arundel, England to Wales and back in 1972. I was 17 and she was 19. We met some great people who gave us rides, invited us in for tea, and one woman in Birmingham who put us up in a lovely bedroom for the night, recalling how her son had been well-treated by strangers when he hitchhiked in South Africa. Looking back, it seems risky but at the time, as you point out, it was acceptable.