Most kids don’t get into some new activity because the activity itself looks cool to them. They get into the activity because someone they think is cool is into it. Never underestimate the power of peer influence (and its more insidious cousin, peer pressure) over kids.
(The practical upshot of this observation is that if you want kids to think yoyoing is cool, have someone they think is cool demo some tricks. Some old fart like me throwing a few Brain Twisters ain’t gonna get it done.)