As a veteran trader (18 years, mostly derivatives) the appeal to forex is simple.
1. leverage with out interest cost.
2. "no commissions"
3. 24 hour market
4. less than 20 Major currency pairs (as opposed to 20,000 plus stocks, mutual funds, ETF's etc.
5. Low capital for entry.
6. Free analytical tools (charting software etc.)
7. The ability to open demo accounts to test ideas, systems etc.
8. wonderful forums where experienced traders share ideas, systems etc. for free.
9. the ability to backtest ideas in an instant without worry.
10. the ability to trade news on a "whole market" instead of trying to identify specific stocks that may be affected.
I could go on but this pretty much sums it up for the hundreds of forex traders I have spoken with.
Seriously