Currency Trading Capital Gains

Is trading or investing worth it?
Is trading or investing in stocks, bonds, currencies, etc worth it? Because as far as I know people can make as much money as they want, but after the TAX, I have hard time believing if they actually get to keep anything in their pockets. The government puts 20% (according to my tax bracket) on capital gains. After all my hard work, I feel like a tight slap in my face. 20% is a lot, and I think it would be even more if you are single and if you trade for short term.
So why do people not get discourage by high taxes; they would have to make a lot of money in order to not be discouraged right?
If you make $25,000 on a $100,000 dollar portfolio and have twenty percent taken off that, then you get to take home $20,000. That’s not too shabby. Having a military that has a budget larger than that of every other country in the world combined, a space program, highways, subsidizing farmers, schools, those things don’t come cheap.
Currency Trading: The Basics