At what point in recent history did pubic hair become a bad thing, and why?

I recently saw an interview with Hugh Hefner, and he was asked about how the porn industry has changed since he started. He said something about none of the girls having pubic hair any more.

Now the trend is waxing, shaving, trimming, etc. (myself included).

when in recent history did pubic hair become a bad thing, and why do you think this happened?