Because I suck, really. You have to be honest with yourself. Are you good enough to manage your own investments? I am not, so far, so I fired myself.
But I still do dabble a little in stocks. Because I want to learn how to trade/invest for myself. I have a pitiful amount of money left in my account that I opened back in 1999 (great timing). I have a Roth IRA that has a little more. My main 'investment' is my 401K and the pro's are investing that.
I currently own one stock. Finisar incorporated (FNSR). I have have some paper profits in it. It was not a good trade, though. I wish I had owned Titanium Metals (TIE) as long as I have owned Finisar.
My problem has been inexperience and poor discipline. I don't sell when I know I should. I should have sold FNSR at 5.25. I could have bought it back at 4.25.
Now the metals are roaring. I should have been in that. Or the oils. Shoulda had Ultra Pete.
But it is easy to tell what you should have done. It is worse when you are right and still get it wrong. I owned Etrade at 4 bucks. It tripped my stop and I never got back in. I new it was right, because a new bull market was starting. It was a cinch that new accounts would open and more trading would happen at Etrade. Etrade went to 15 bucks pretty quickly. Now it is at 24.
My efforts have had less than stellar results so far. I have sent myself back to the minors. Well, actually I never made it to the majors. If I never do get there, I will be fine. But I am not going to quit either.
Note: To see what I am talking about with UPL and TIE look at the weekly charts.