These things ebb and flow - I see more kids on scooters and BMX bikes locally than I do skateboards now. Rollerskates and quad skates have come back in a big way, especially for aggressive skating. Skateboarding also seems to have fragmented into street surfing, longboarding, and a bunch of other disciplines that have different equipment and techniques.

That's pretty much the thesis of the video that browningstreet posted a link to posited as well. I'm not sure that explains though the casual 30 to 40 somethings who did it pretty regularly until they pretty much dropped it though. I'm not even sure why I did other than the fact that fewer people I knew were looking to do it as a recreational activity so it became less and less an activity I even thought about.

I probably go with fashion/fad at the end of the day.