I love pinball now, but I HATED it as a kid and teenager. I'd often frequent my local bowling alley, which had an arcade of maybe 20 machines. Most were video games, about 4 were pinball machines. I'd put a few quarters in a pin (High Speed) and drain almost immediately. I didn't know how to play, didn't know where the points were, and only wanted to hit stuff to see the lights and sounds. I couldn't keep the ball alive long enough to even do that. Maybe I wasn't coordinated enough as a kid? I hated it. I stuck to the video games. They were constant action and I didn't need to think, I just needed to react. No learning required.
Fast forward 15 years: I find myself in front of another pinball machine (Ripley's Believe It Or Not). I was able to keep the ball alive and hit stuff. I was required to think and analyze, and use my coordination to hit the intended shots. I had a specific plan in place and executed it to the best of my ability. I learned bumping and nudging over time, and all the other nuances and tricks that come along with pinball, and I'm still learning them to this day. It's a constant learning experience and I enjoy it greatly.
Point is, I think kids aren't interested in pinball because being good requires a thought process, knowledge, and skill. All of this requires time and effort. Kids' brains haven't developed their frontal lobes enough to be interested in things that require such things (the majority of kids, anyway). Some do, most don't. We've all been this way. How many of us had a love of learning as a kid? How many of us have a love of learning today? I'll bet it's close to the same for all of us. As we've grown older, we've taking a liking to the challenging things in life, the ones that require time, effort, skill, thought, etc.
Pinball won't die. In fact, with the increase in video games such as zen pinball and pinball arcade, the younger generation will be more inclined to join the hobby as an adult. They will be more familiar with it, and therefore won't be afraid to attempt it when the moment arises.
My 2 cents.