For me it was pure curiosity. I never thought about being rich or driving a Ferrari or anything like that, it was obvious to me that to make serious money you'd also have to risk serious money.
I would occasionally hear that the price of oil had gone up, or the dollar had fallen and I wanted to understand how and why that happened. I was pleasantly surprised to find that ordinary folk could trade on stock and currency markets, so I gave it a go. MUCH harder than I expected, came close to giving up a few times. At last I developed a profitable strategy, and more importantly, I learned HOW to develop profitable strategies. But there are no shortcuts, it's just hard work.