For me it was Fireworks and the Scientific Method, I like launching things, my country has banned rockets but I grew up with them, and the explosions are a chance to learn from the mistakes made
KSP allows me to play with virtual fireworks, removing the risk of physical injury, and learn some things in the process, not burn down the neighborhood, and have a laugh doing so. It's a win-win-win-win-win.
Zoom, boom!
Freddy