I wouldn't say lucid dreaming was ever "popular", per se. I mean, I first learned about it back when I was a senior in high school...which was back in '06. On my final day of class, my English teacher (who was awesome) told the class about it. I'll bet anything that out of that entire class, I was the only one who ever went on to pursue lucid dreaming.

But then again, can you really blame people for giving up on LDing so early on? It's not something attributable to simple laziness - I've personally found that the more I actively try to LD, the more sleep I lose, and considering the average American only gets 7 hours of sleep (which is almost not enough), you can't really fault people on not wanting to invest their valuable sleep time.